Python Borg pattern 模式疑问

from typing import Dict


class Borg:
    _shared_state: Dict[str, str] = {}

    def __init__(self):
        self.__dict__ = self._shared_state


class YourBorg(Borg):
    def __init__(self, state=None):
        super().__init__()
        if state:
            self.state = state
        else:
            # initiate the first instance with default state
            if not hasattr(self, "state"):
                self.state = "Init"   # 这里为什么会更新到 _shared_state 的 value 中

    def __str__(self):
        return self.state

第 19 行, self.state = "Init" 后, 会将_shared_state: {}, 更新为 _shared_state: {"state": "Init"} 这是为什么?