Hi,

It seems that two fields in inspect.FullArgSpec are mis-annotated:

Looking at the implementation of getfullargspec, at the very end this happens:

    if not kwdefaults:
        # compatibility with 'func.__kwdefaults__'
        kwdefaults = None

    if not defaults:
        # compatibility with 'func.__defaults__'
        defaults = None

The two fields kwonlydefaults and defaults need to be Optional[]. This seems to be true for Python 3.4+:

• https://github.com/python/cpython/blob/3.4/Lib/inspect.py
• https://github.com/python/cpython/blob/3.5/Lib/inspect.py
• https://github.com/python/cpython/blob/3.6/Lib/inspect.py
• https://github.com/python/cpython/blob/3.7/Lib/inspect.py
• https://github.com/python/cpython/blob/3.8/Lib/inspect.py