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 serialize(self):
        s = []
        for v in self:
            if isinstance(v, BaseConfig):
                v = v.serialize()
            s.append(v)
        return s