def followed_topics(self):
        """获取用户关注的话题.

        :return: 用户关注的话题，返回生成器
        :rtype: Topic.Iterable
        """
        from .topic import Topic
        if self.url is None:
            return
        if self.followed_topic_num > 0:
            tag = self.soup.find('div', class_='zm-profile-side-topics')
            if tag is not None:
                for a in tag.find_all('a'):
                    yield Topic(Zhihu_URL + a['href'], a.img['alt'],
                                session=self._session)
            if self.followed_topic_num > 7:
                offset = 7
                gotten_data_num = 20
                while gotten_data_num == 20:
                    data = {'start': 0, 'offset': offset, '_xsrf': self.xsrf}
                    j = self._session.post(
                        Author_Get_More_Follow_Topic_URL.format(self.id),
                        data=data).json()
                    gotten_data_num = j['msg'][0]
                    offset += gotten_data_num
                    topic_item = BeautifulSoup(j['msg'][1]).find_all(
                        'div', class_='zm-profile-section-item')
                    for div in topic_item:
                        name = div.strong.text
                        url = Zhihu_URL + div.a['href']
                        yield Topic(url, name, session=self._session)
获取用户关注的话题.

        :return: 用户关注的话题，返回生成器
        :rtype: Topic.Iterable