Python为类自身添加类型注解

只需from __future__ import annotations

例如：

from __future__ import annotations

class Position:
    def __add__(self, other: Position) -> Position:
        ...

来源：
https://stackoverflow.com/questions/33533148/how-do-i-type-hint-a-method-with-the-type-of-the-enclosing-class/33533514#33533514