def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def __init__(self, root_path: str, defaults: t.Optional[dict] = None) -> None:
        dict.__init__(self, defaults or {})
        self.root_path = root_path