python容易出错的返回值

class _ActionsContainer(object):
    def __init__(self):
        self._registries = {}

    def register(self, registry_name, value, object):
        registry = self._registries.setdefault(registry_name, {}) #此处setdefault参数相当于key，vaule，最终返回value，次value与registry共享内存
        print(registry)
        print(self._registries)
        registry[value] = object

if __name__ == '__main__':
    action = _ActionsContainer()
    action.register('action', None,  'xxx')
    #打印结果？