code: def remove_topic(self, topic_id):
          
          comment_start = 0
          while comment_start is not None:
              comments = self.list_comments(topic_id, comment_start)
              for comment in comments['results']:
                  self.remove_comment(topic_id, comment['id'])
              comment_start = comments['next_start']
          return self.api.req(API_GROUP_REMOVE_TOPIC % topic_id, params={'ck': self.api.ck()})
docs: 删除话题（需要先删除所有评论，使用默认参数）
          
          :param topic_id: 话题ID
          :return: None