Shared via mypy Playground

main.py

import enum
import functools
import typing as t


class Color(enum.Enum):
    RED = enum.auto()
    
    @enum.nonmember
    @functools.cache
    def lowercase_name(self) -> str:
        return self.name.lower()


t.assert_type(Color.RED.value, int)  # works


def frobnicate(color: Color) -> None:
    t.assert_type(color.value, int)