from typing import Generic, TypeVar, Any, overload

AnyStr = TypeVar("AnyStr", str, bytes)

class Popen(Generic[AnyStr]):
    @overload
    def communicate(self: Popen[str], buf: str = ...) -> float: ...
    @overload
    def communicate(self: Popen[bytes], buf: memoryview | bytes = ...) -> range: ...
    def communicate(self, buf: object = None) -> Any: raise NotImplementedError

p = Popen()
reveal_type(p.communicate())