Python typing: How to use Generic?

Question

Consider the following example:

import typing

T = typing.TypeVar('T', bound=typing.Union[int, bool, str])

class Test(typing.Generic[T]):

    def __init__(self, v: T) -> None:
        self.v = v
        self.t = type(v)

    def parse(self, s: str) -> T:
        if self.t == int:
            return int(s, base=0)
        elif self.t == bool:
            return s.lower() != 'false'
        elif self.t == str:
            return s
        else:
            raise NotImplementedError()

mypy complains:

test.py:13: error: Incompatible return value type (got "int", expected "T")
test.py:15: error: Incompatible return value type (got "bool", expected "T")
test.py:17: error: Incompatible return value type (got "str", expected "T")

How do I rewrite the code so that mypy understands that T is in this case int/bool/str?