Extract `__func__` attribute from staticmethod/classmethod descriptors
before treating them as callables. Python's `@staticmethod` and
`@classmethod` decorators wrap methods in descriptor objects that are
not directly usable as PythonCallable, when calling PyCallable_Check.
The actual callable function is stored in the `__func__` attribute of
these descriptors, so we need to unwrap them to properly validate and
invoke the decorated methods in scripted interfaces.
Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>
3ca85e74a1