# Firebase Hosting API . projects . sites . releases

## Instance Methods

Creates a new release which makes the content of the specified version

Lists the releases that have been created on the specified site.

Retrieves the next page of results.

### Method Details

`create(parent, body=None, versionName=None, x__xgafv=None)`

    Creates a new release which makes the content of the specified version
    actively display on the appropriate URL(s).

    Args:
      parent: string, Required. The site that the release belongs to, in the format:
    <code>sites/<var>site-name</var></code> (required)
      body: object, The request body.
        The object takes the form of:

    { # A `Release` is a particular
        # [collection of configurations and files](sites.versions)
        # that is set to be public at a particular time.
      "version": { # A `Version` is the collection of configuration and # Output only. The configuration and content that was released.
          # [static files](sites.versions.files) that determine how a site is displayed.
        "deleteUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who `DELETED` the version.
            # a release or finalizing a version.
          "email": "A String", # The email address of the user when the user performed the action.
          "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
              # changed their email address or deleted their account.
        },
        "finalizeUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who `FINALIZED` the version.
            # a release or finalizing a version.
          "email": "A String", # The email address of the user when the user performed the action.
          "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
              # changed their email address or deleted their account.
        },
        "deleteTime": "A String", # Output only. The time at which the version was `DELETED`.
        "preview": { # Version preview configuration. If active and unexpired, # Version preview configuration for the site version. This configuration
            # specfies whether previewing is enabled for this site version. Version
            # previews allow you to preview your site at a custom URL before
            # releasing it as the live version.
            # this version will be accessible via a custom URL even
            # if it is not the currently released version.
          "active": True or False, # If true, preview URLs are enabled for this version.
          "expireTime": "A String", # Indicates the expiration time for previewing this
              # version; preview URL requests received after this time will 404.
        },
        "labels": { # The labels used for extra metadata and/or filtering.
          "a_key": "A String",
        },
        "createTime": "A String", # Output only. The time at which the version was created.
        "versionBytes": "A String", # Output only. The total stored bytesize of the version.
            # <br>This value is calculated after a version is `FINALIZED`.
        "finalizeTime": "A String", # Output only. The time at which the version was `FINALIZED`.
        "status": "A String", # The deploy status of a version.
            # <br>
            # <br>For a successful deploy, call the
            # [`CreateVersion`](sites.versions/create) endpoint to make a new version
            # (`CREATED` status),
            # [upload all desired files](sites.versions/populateFiles) to the version,
            # then [update](sites.versions/patch) the version to the `FINALIZED` status.
            # <br>
            # <br>Note that if you leave the version in the `CREATED` state for more
            # than 12&nbsp;hours, the system will automatically mark the version as
            # `ABANDONED`.
            # <br>
            # <br>You can also change the status of a version to `DELETED` by calling the
            # [`DeleteVersion`](sites.versions/delete) endpoint.
        "config": { # The configuration for how incoming requests to a site should be routed and # The configuration for the behavior of the site. This configuration exists
            # in the [`firebase.json`](/docs/cli/#the_firebasejson_file) file.
            # processed before serving content. The patterns are matched and applied
            # according to a specific
            # [priority order](/docs/hosting/full-config#hosting_priority_order).
          "redirects": [ # A list of globs that will cause the response to redirect to another
              # location.
            { # A [`redirect`](/docs/hosting/full-config#redirects) represents the
                # configuration for returning an HTTP redirect response given a matching
                # request URL path.
              "glob": "A String", # The user-supplied [glob
                  # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                  # against the request URL path.
              "statusCode": 42, # Required. The status HTTP code to return in the response. It must be a
                  # valid 3xx status code.
              "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                  # URL path.
              "location": "A String", # Required. The value to put in the HTTP location header of the response.
                  # <br>The location can contain capture group values from the pattern using
                  # a `:` prefix to identify the segment and an optional `*` to capture the
                  # rest of the URL.
                  # For example:
                  # <code>"glob": "/:capture*",
                  # <br>"statusCode": 301,
                  # <br>"location": "https://example.com/foo/:capture"</code>
            },
          ],
          "headers": [ # A list of custom response headers that are added to the content if the
              # request URL path matches the glob.
            { # A [`header`](/docs/hosting/full-config#headers) defines custom headers to
                # add to a response should the request URL path match the pattern.
              "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                  # URL path.
              "glob": "A String", # The user-supplied [glob
                  # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                  # against the request URL path.
              "headers": { # Required. The additional headers to add to the response.
                "a_key": "A String",
              },
            },
          ],
          "appAssociation": "A String", # How to handle well known App Association files.
          "trailingSlashBehavior": "A String", # Defines how to handle a trailing slash in the URL path.
          "cleanUrls": True or False, # Defines whether to drop the file extension from uploaded files.
          "rewrites": [ # A list of rewrites that will act as if the service were given the
              # destination URL.
            { # A [`rewrite`](/docs/hosting/full-config#rewrites) represents an internal
                # content rewrite on the version. If the pattern matches, the request will be
                # handled as if it were to the destination path specified in the
                # configuration.
              "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                  # URL path.
              "dynamicLinks": True or False, # The request will be forwarded to Firebase Dynamic Links.
              "run": { # A configured rewrite that directs requests to a Cloud Run service. If the # The request will be forwarded to Cloud Run.
                  # Cloud Run service does not exist when setting or updating your Firebase
                  # Hosting configuration, then the request fails. Any errors from the Cloud Run
                  # service are passed to the end user (for example, if you delete a service, any
                  # requests directed to that service receive a `404` error).
                "region": "A String", # Optional. User-provided region where the Cloud Run service is hosted.<br>
                    # Defaults to `us-central1` if not supplied.
                "serviceId": "A String", # Required. User-defined ID of the Cloud Run service.
              },
              "glob": "A String", # The user-supplied [glob
                  # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                  # against the request URL path.
              "path": "A String", # The URL path to rewrite the request to.
              "function": "A String", # The function to proxy requests to. Must match the exported function
                  # name exactly.
            },
          ],
        },
        "name": "A String", # The unique identifier for a version, in the format:
            # <code>sites/<var>site-name</var>/versions/<var>versionID</var></code>
            # This name is provided in the response body when you call the
            # [`CreateVersion`](../sites.versions/create) endpoint.
        "createUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who created the version.
            # a release or finalizing a version.
          "email": "A String", # The email address of the user when the user performed the action.
          "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
              # changed their email address or deleted their account.
        },
        "fileCount": "A String", # Output only. The total number of files associated with the version.
            # <br>This value is calculated after a version is `FINALIZED`.
      },
      "message": "A String", # The deploy description when the release was created. The value can be up to
          # 512&nbsp;characters.
      "releaseUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who created the release.
          # a release or finalizing a version.
        "email": "A String", # The email address of the user when the user performed the action.
        "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
            # changed their email address or deleted their account.
      },
      "releaseTime": "A String", # Output only. The time at which the version is set to be public.
      "name": "A String", # Output only. The unique identifier for the release, in the format:
          # <code>sites/<var>site-name</var>/releases/<var>releaseID</var></code>
          # This name is provided in the response body when you call the
          # [`CreateRelease`](sites.releases/create) endpoint.
      "type": "A String", # Explains the reason for the release.
          # <br>Specify a value for this field only when creating a `SITE_DISABLE`
          # type release.
    }

      versionName: string, The unique identifier for a version, in the format:
    <code>/sites/<var>site-name</var>/versions/<var>versionID</var></code>
    The <var>site-name</var> in this version identifier must match the
    <var>site-name</var> in the `parent` parameter.
    <br>
    <br>This query parameter must be empty if the `type` field in the
    request body is `SITE_DISABLE`.
      x__xgafv: string, V1 error format.
        Allowed values
          1 - v1 error format
          2 - v2 error format

    Returns:
      An object of the form:

        { # A `Release` is a particular
          # [collection of configurations and files](sites.versions)
          # that is set to be public at a particular time.
        "version": { # A `Version` is the collection of configuration and # Output only. The configuration and content that was released.
            # [static files](sites.versions.files) that determine how a site is displayed.
          "deleteUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who `DELETED` the version.
              # a release or finalizing a version.
            "email": "A String", # The email address of the user when the user performed the action.
            "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                # changed their email address or deleted their account.
          },
          "finalizeUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who `FINALIZED` the version.
              # a release or finalizing a version.
            "email": "A String", # The email address of the user when the user performed the action.
            "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                # changed their email address or deleted their account.
          },
          "deleteTime": "A String", # Output only. The time at which the version was `DELETED`.
          "preview": { # Version preview configuration. If active and unexpired, # Version preview configuration for the site version. This configuration
              # specfies whether previewing is enabled for this site version. Version
              # previews allow you to preview your site at a custom URL before
              # releasing it as the live version.
              # this version will be accessible via a custom URL even
              # if it is not the currently released version.
            "active": True or False, # If true, preview URLs are enabled for this version.
            "expireTime": "A String", # Indicates the expiration time for previewing this
                # version; preview URL requests received after this time will 404.
          },
          "labels": { # The labels used for extra metadata and/or filtering.
            "a_key": "A String",
          },
          "createTime": "A String", # Output only. The time at which the version was created.
          "versionBytes": "A String", # Output only. The total stored bytesize of the version.
              # <br>This value is calculated after a version is `FINALIZED`.
          "finalizeTime": "A String", # Output only. The time at which the version was `FINALIZED`.
          "status": "A String", # The deploy status of a version.
              # <br>
              # <br>For a successful deploy, call the
              # [`CreateVersion`](sites.versions/create) endpoint to make a new version
              # (`CREATED` status),
              # [upload all desired files](sites.versions/populateFiles) to the version,
              # then [update](sites.versions/patch) the version to the `FINALIZED` status.
              # <br>
              # <br>Note that if you leave the version in the `CREATED` state for more
              # than 12&nbsp;hours, the system will automatically mark the version as
              # `ABANDONED`.
              # <br>
              # <br>You can also change the status of a version to `DELETED` by calling the
              # [`DeleteVersion`](sites.versions/delete) endpoint.
          "config": { # The configuration for how incoming requests to a site should be routed and # The configuration for the behavior of the site. This configuration exists
              # in the [`firebase.json`](/docs/cli/#the_firebasejson_file) file.
              # processed before serving content. The patterns are matched and applied
              # according to a specific
              # [priority order](/docs/hosting/full-config#hosting_priority_order).
            "redirects": [ # A list of globs that will cause the response to redirect to another
                # location.
              { # A [`redirect`](/docs/hosting/full-config#redirects) represents the
                  # configuration for returning an HTTP redirect response given a matching
                  # request URL path.
                "glob": "A String", # The user-supplied [glob
                    # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                    # against the request URL path.
                "statusCode": 42, # Required. The status HTTP code to return in the response. It must be a
                    # valid 3xx status code.
                "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                    # URL path.
                "location": "A String", # Required. The value to put in the HTTP location header of the response.
                    # <br>The location can contain capture group values from the pattern using
                    # a `:` prefix to identify the segment and an optional `*` to capture the
                    # rest of the URL.
                    # For example:
                    # <code>"glob": "/:capture*",
                    # <br>"statusCode": 301,
                    # <br>"location": "https://example.com/foo/:capture"</code>
              },
            ],
            "headers": [ # A list of custom response headers that are added to the content if the
                # request URL path matches the glob.
              { # A [`header`](/docs/hosting/full-config#headers) defines custom headers to
                  # add to a response should the request URL path match the pattern.
                "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                    # URL path.
                "glob": "A String", # The user-supplied [glob
                    # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                    # against the request URL path.
                "headers": { # Required. The additional headers to add to the response.
                  "a_key": "A String",
                },
              },
            ],
            "appAssociation": "A String", # How to handle well known App Association files.
            "trailingSlashBehavior": "A String", # Defines how to handle a trailing slash in the URL path.
            "cleanUrls": True or False, # Defines whether to drop the file extension from uploaded files.
            "rewrites": [ # A list of rewrites that will act as if the service were given the
                # destination URL.
              { # A [`rewrite`](/docs/hosting/full-config#rewrites) represents an internal
                  # content rewrite on the version. If the pattern matches, the request will be
                  # handled as if it were to the destination path specified in the
                  # configuration.
                "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                    # URL path.
                "dynamicLinks": True or False, # The request will be forwarded to Firebase Dynamic Links.
                "run": { # A configured rewrite that directs requests to a Cloud Run service. If the # The request will be forwarded to Cloud Run.
                    # Cloud Run service does not exist when setting or updating your Firebase
                    # Hosting configuration, then the request fails. Any errors from the Cloud Run
                    # service are passed to the end user (for example, if you delete a service, any
                    # requests directed to that service receive a `404` error).
                  "region": "A String", # Optional. User-provided region where the Cloud Run service is hosted.<br>
                      # Defaults to `us-central1` if not supplied.
                  "serviceId": "A String", # Required. User-defined ID of the Cloud Run service.
                },
                "glob": "A String", # The user-supplied [glob
                    # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                    # against the request URL path.
                "path": "A String", # The URL path to rewrite the request to.
                "function": "A String", # The function to proxy requests to. Must match the exported function
                    # name exactly.
              },
            ],
          },
          "name": "A String", # The unique identifier for a version, in the format:
              # <code>sites/<var>site-name</var>/versions/<var>versionID</var></code>
              # This name is provided in the response body when you call the
              # [`CreateVersion`](../sites.versions/create) endpoint.
          "createUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who created the version.
              # a release or finalizing a version.
            "email": "A String", # The email address of the user when the user performed the action.
            "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                # changed their email address or deleted their account.
          },
          "fileCount": "A String", # Output only. The total number of files associated with the version.
              # <br>This value is calculated after a version is `FINALIZED`.
        },
        "message": "A String", # The deploy description when the release was created. The value can be up to
            # 512&nbsp;characters.
        "releaseUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who created the release.
            # a release or finalizing a version.
          "email": "A String", # The email address of the user when the user performed the action.
          "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
              # changed their email address or deleted their account.
        },
        "releaseTime": "A String", # Output only. The time at which the version is set to be public.
        "name": "A String", # Output only. The unique identifier for the release, in the format:
            # <code>sites/<var>site-name</var>/releases/<var>releaseID</var></code>
            # This name is provided in the response body when you call the
            # [`CreateRelease`](sites.releases/create) endpoint.
        "type": "A String", # Explains the reason for the release.
            # <br>Specify a value for this field only when creating a `SITE_DISABLE`
            # type release.
      }

`list(parent, pageToken=None, pageSize=None, x__xgafv=None)`

    Lists the releases that have been created on the specified site.

    Args:
      parent: string, Required. The parent for which to list files, in the format:
    <code>sites/<var>site-name</var></code> (required)
      pageToken: string, The next_page_token from a previous request, if provided.
      pageSize: integer, The page size to return. Defaults to 100.
      x__xgafv: string, V1 error format.
        Allowed values
          1 - v1 error format
          2 - v2 error format

    Returns:
      An object of the form:

        {
        "releases": [ # The list of hashes of files that still need to be uploaded, if any exist.
          { # A `Release` is a particular
              # [collection of configurations and files](sites.versions)
              # that is set to be public at a particular time.
            "version": { # A `Version` is the collection of configuration and # Output only. The configuration and content that was released.
                # [static files](sites.versions.files) that determine how a site is displayed.
              "deleteUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who `DELETED` the version.
                  # a release or finalizing a version.
                "email": "A String", # The email address of the user when the user performed the action.
                "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                    # changed their email address or deleted their account.
              },
              "finalizeUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who `FINALIZED` the version.
                  # a release or finalizing a version.
                "email": "A String", # The email address of the user when the user performed the action.
                "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                    # changed their email address or deleted their account.
              },
              "deleteTime": "A String", # Output only. The time at which the version was `DELETED`.
              "preview": { # Version preview configuration. If active and unexpired, # Version preview configuration for the site version. This configuration
                  # specfies whether previewing is enabled for this site version. Version
                  # previews allow you to preview your site at a custom URL before
                  # releasing it as the live version.
                  # this version will be accessible via a custom URL even
                  # if it is not the currently released version.
                "active": True or False, # If true, preview URLs are enabled for this version.
                "expireTime": "A String", # Indicates the expiration time for previewing this
                    # version; preview URL requests received after this time will 404.
              },
              "labels": { # The labels used for extra metadata and/or filtering.
                "a_key": "A String",
              },
              "createTime": "A String", # Output only. The time at which the version was created.
              "versionBytes": "A String", # Output only. The total stored bytesize of the version.
                  # <br>This value is calculated after a version is `FINALIZED`.
              "finalizeTime": "A String", # Output only. The time at which the version was `FINALIZED`.
              "status": "A String", # The deploy status of a version.
                  # <br>
                  # <br>For a successful deploy, call the
                  # [`CreateVersion`](sites.versions/create) endpoint to make a new version
                  # (`CREATED` status),
                  # [upload all desired files](sites.versions/populateFiles) to the version,
                  # then [update](sites.versions/patch) the version to the `FINALIZED` status.
                  # <br>
                  # <br>Note that if you leave the version in the `CREATED` state for more
                  # than 12&nbsp;hours, the system will automatically mark the version as
                  # `ABANDONED`.
                  # <br>
                  # <br>You can also change the status of a version to `DELETED` by calling the
                  # [`DeleteVersion`](sites.versions/delete) endpoint.
              "config": { # The configuration for how incoming requests to a site should be routed and # The configuration for the behavior of the site. This configuration exists
                  # in the [`firebase.json`](/docs/cli/#the_firebasejson_file) file.
                  # processed before serving content. The patterns are matched and applied
                  # according to a specific
                  # [priority order](/docs/hosting/full-config#hosting_priority_order).
                "redirects": [ # A list of globs that will cause the response to redirect to another
                    # location.
                  { # A [`redirect`](/docs/hosting/full-config#redirects) represents the
                      # configuration for returning an HTTP redirect response given a matching
                      # request URL path.
                    "glob": "A String", # The user-supplied [glob
                        # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                        # against the request URL path.
                    "statusCode": 42, # Required. The status HTTP code to return in the response. It must be a
                        # valid 3xx status code.
                    "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                        # URL path.
                    "location": "A String", # Required. The value to put in the HTTP location header of the response.
                        # <br>The location can contain capture group values from the pattern using
                        # a `:` prefix to identify the segment and an optional `*` to capture the
                        # rest of the URL.
                        # For example:
                        # <code>"glob": "/:capture*",
                        # <br>"statusCode": 301,
                        # <br>"location": "https://example.com/foo/:capture"</code>
                  },
                ],
                "headers": [ # A list of custom response headers that are added to the content if the
                    # request URL path matches the glob.
                  { # A [`header`](/docs/hosting/full-config#headers) defines custom headers to
                      # add to a response should the request URL path match the pattern.
                    "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                        # URL path.
                    "glob": "A String", # The user-supplied [glob
                        # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                        # against the request URL path.
                    "headers": { # Required. The additional headers to add to the response.
                      "a_key": "A String",
                    },
                  },
                ],
                "appAssociation": "A String", # How to handle well known App Association files.
                "trailingSlashBehavior": "A String", # Defines how to handle a trailing slash in the URL path.
                "cleanUrls": True or False, # Defines whether to drop the file extension from uploaded files.
                "rewrites": [ # A list of rewrites that will act as if the service were given the
                    # destination URL.
                  { # A [`rewrite`](/docs/hosting/full-config#rewrites) represents an internal
                      # content rewrite on the version. If the pattern matches, the request will be
                      # handled as if it were to the destination path specified in the
                      # configuration.
                    "regex": "A String", # The user-supplied RE2 regular expression to match against the request
                        # URL path.
                    "dynamicLinks": True or False, # The request will be forwarded to Firebase Dynamic Links.
                    "run": { # A configured rewrite that directs requests to a Cloud Run service. If the # The request will be forwarded to Cloud Run.
                        # Cloud Run service does not exist when setting or updating your Firebase
                        # Hosting configuration, then the request fails. Any errors from the Cloud Run
                        # service are passed to the end user (for example, if you delete a service, any
                        # requests directed to that service receive a `404` error).
                      "region": "A String", # Optional. User-provided region where the Cloud Run service is hosted.<br>
                          # Defaults to `us-central1` if not supplied.
                      "serviceId": "A String", # Required. User-defined ID of the Cloud Run service.
                    },
                    "glob": "A String", # The user-supplied [glob
                        # pattern](/docs/hosting/full-config#glob_pattern_matching) to match
                        # against the request URL path.
                    "path": "A String", # The URL path to rewrite the request to.
                    "function": "A String", # The function to proxy requests to. Must match the exported function
                        # name exactly.
                  },
                ],
              },
              "name": "A String", # The unique identifier for a version, in the format:
                  # <code>sites/<var>site-name</var>/versions/<var>versionID</var></code>
                  # This name is provided in the response body when you call the
                  # [`CreateVersion`](../sites.versions/create) endpoint.
              "createUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who created the version.
                  # a release or finalizing a version.
                "email": "A String", # The email address of the user when the user performed the action.
                "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                    # changed their email address or deleted their account.
              },
              "fileCount": "A String", # Output only. The total number of files associated with the version.
                  # <br>This value is calculated after a version is `FINALIZED`.
            },
            "message": "A String", # The deploy description when the release was created. The value can be up to
                # 512&nbsp;characters.
            "releaseUser": { # Contains metadata about the user who performed an action, such as creating # Output only. Identifies the user who created the release.
                # a release or finalizing a version.
              "email": "A String", # The email address of the user when the user performed the action.
              "imageUrl": "A String", # A profile image URL for the user. May not be present if the user has
                  # changed their email address or deleted their account.
            },
            "releaseTime": "A String", # Output only. The time at which the version is set to be public.
            "name": "A String", # Output only. The unique identifier for the release, in the format:
                # <code>sites/<var>site-name</var>/releases/<var>releaseID</var></code>
                # This name is provided in the response body when you call the
                # [`CreateRelease`](sites.releases/create) endpoint.
            "type": "A String", # Explains the reason for the release.
                # <br>Specify a value for this field only when creating a `SITE_DISABLE`
                # type release.
          },
        ],
        "nextPageToken": "A String", # If there are additional releases remaining beyond the ones in this
            # response, then supply this token in the next
            # [`list`](../sites.versions.files/list) call to continue with the next set
            # of releases.
      }

`list_next(previous_request, previous_response)`

    Retrieves the next page of results.

    Args:
      previous_request: The request for the previous page. (required)
      previous_response: The response from the request for the previous page. (required)

    Returns:
      A request object that you can call 'execute()' on to request the next
      page. Returns None if there are no more items in the collection.