I'm not sure if you're aiming for exact compatibility among python versions for all of the functions you support or not.

But due to python/cpython#90353, get_type_hints with include_extras=True has inconsistent behavior among python versions below 3.11.

• def foo(bar: Annotated[Union[int, None]]) -> Annotated[Union[int, None]]
• def foo(bar: Annotated[Union[int, None]] = None) -> Optional[Annotated[Union[int, None]]]

I see #94, which mentions not wanting to do more rigorous porting due to it cascading into more code needing to be pulled in, so I'm not sure what the reaction to this will be...