on_snapshot defined in DocumentReference documentation is inconsistent with those of Watch and Product Documentation.

In DocumentReference documentation, we have

and

In Watch documentation, we have

In Product Documentation, we have

# Create a callback on_snapshot function to capture changes
def on_snapshot(doc_snapshot, changes, read_time):
    for doc in doc_snapshot:
        print(u'Received document snapshot: {}'.format(doc.id))

doc_ref = db.collection(u'cities').document(u'SF')

# Watch the document
doc_watch = doc_ref.on_snapshot(on_snapshot)

The function signature in DocumentReference takes 1 argument, but the function signature in Watch and Product Documentation takes 3 arguments. Are these referring to the same function? If so, the documentation in DocumentReference may be updated to reflect these changes. If not, on_snapshot in Product Documentation may be renamed to a different name than on_snapshot in DocumentReference to be more clear.

Will probably submit a pull request to update documentation in DocumentReference to be consistent with that in Watch.

Thanks!