def refresh(self):
super().refresh()<EOL>self._html = None<EOL>self._title = None<EOL>self._details = None<EOL>self._answer_num = None<EOL>self._follower_num = None<EOL>self._topics = None<EOL>self._last_edit_time = None<EOL>self._logs = None<EOL>
刷新 Question object 的属性. 
        例如回答数增加了, 先调用 ``refresh()`` 
        再访问 answer_num 属性, 可获得更新后的答案数量.

        :return: None