check generics for mypy

stack.py

from typing import TypeVar, Generic

T = TypeVar('T', bound='Shape')

class Stack(Generic[T]):
    def __init__(self) -> None:
        # Create an empty list with items of type a T
        print(__annotations__) # {}
        self.items: List[T] = []

stack:Stack[int] = Stack[int]()
print(__annotations__) # {'stack': __main__.Stack[int]}