python类中方法返回自身值类型的写法

在python3中使用类型遇到的问题，代码如下：

想在factory创建自已，以为类型是这样的-> People

class People:
    name: str

    def __init__(self, name: str) -> None:
        self.name = name

    @classmethod
    def factory(cls, name: str) -> People:
        return cls(name)

这样的错的

正确的写法是这样的：

from typing import TypeVar, Type

T = TypeVar('T', bound='People')

class People:
    name: str

    def __init__(self, name: str) -> None:
        self.name = name

    @classmethod
    def factory(cls: Type[T], name: str) -> T:
        return cls(name)

要写成泛型才对，问题地址：https://github.com/python/peps/pull/89

另一种方法

类型写成字符串也是可以的

class People:
    name: str

    def __init__(self, name: str) -> None:
        self.name = name

    @classmethod
    def factory(cls, name: str) -> "People":
        return cls(name)