from typing_extensions import Protocol
from typing import overload, Any, Callable, Generic, Tuple, TypeVar

T = TypeVar("T", contravariant=True)
U = TypeVar("U", covariant=True)

class HasGetItem(Protocol, Generic[T, U]):
    def __getitem__(self, item: T) -> U: ...


class Foo(HasGetItem[int, str]): ...

foo = Foo()
foo[41]
foo["41"]  # E: Invalid index type "str" for "Foo"; expected type "int"

foo[42].strip()
foo[42] + 1  # E: Unsupported operand types for + ("str" and "int")

@overload
def itemgetter(item: T) -> Callable[[HasGetItem[T, U]], U]: ...
@overload
def itemgetter(*items: T) -> Callable[[HasGetItem[T, U]], Tuple[U, ...]]: ...