There are a few features missing from the Cython Lexer, or where definitions from the Python Lexer differ (e.g. Name.Builtin.Pseudo). Here is a list of various enhancements that can be made:

1. Include the missing keyword "new", used in C++ mode, within "keyword" context.
2. Define Keyword.Constant token (within "keyword" context) to include:

(words(("True", "False", "None", "NULL"), suffix=r"\b"), Keyword.Constant)

3. Update Name.Builtin.Pseudo token (within "builtins" context) to exclude Keyword.Constant values:

(r"(?<!\.)(self|cls|Ellipsis|NotImplemented)\b", Name.Builtin.Pseudo)

4. Include Missing data types in Builtin token defintion:
   a. char
   b. size_t
   c. ssize_t
   d. double

5. Modify "cdef" context to discriminate between class, function, and variable name tokens. Currently, everything defaults to Name.Function token. Also include missing "packed" and "cppclass" keywords. Something like this:

[
(r"(public|readonly|extern|api|inline|packed)\b", Keyword.Reserved),
(
    r"(struct|enum|union|class|cppclass)\b(\s+)([a-zA-Z_]\w*)",
    bygroups(Keyword, Whitespace, Name.Class),
    "#pop",
),
(r"([a-zA-Z_]\w*)(\s*)(?=\()", bygroups(Name.Function, Whitespace), "#pop"),
(r"([a-zA-Z_]\w*)(\s*)(?=[:,=#\n]|$)", bygroups(Name.Variable, Whitespace), "#pop"),
(r"([a-zA-Z_]\w*)(\s*)(,)", bygroups(Name.Variable, Whitespace, Punctuation)),
... # the rest of context would remain the same
]