Python 3.7.3 (default, Jul 25 2020, 13:03:44) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> str.__new__
<built-in method __new__ of type object at 0x81ec40>
>>> str.__init__
<slot wrapper '__init__' of 'object' objects>
>>> 

from enum import Enum
from typing import TYPE_CHECKING

if not TYPE_CHECKING:
    reveal_type = print

class I(int, Enum):
    a = 1
reveal_type(I['a'])  # E: Revealed type is '__main__.I'

class S(str, Enum):
    a = '1'
reveal_type(S['a'])  # E: Revealed type is '__main__.S'

class F(float, Enum):
    a = 1.0
reveal_type(F['a'])  # E: Revealed type is '__main__.F'

        @overload
        def __new__(cls: Type[_T], o: object = ...) -> _T: ...
        @overload
        def __new__(cls: Type[_T], o: bytes, encoding: str = ..., errors: str = ...) -> _T: ...