code: def followed_topics(self):
          
          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)
docs: 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