code: def answer_num(self):
          
          answer_num_block = self.soup.find('h3', id='zh-question-answer-num')
          # 当0人回答或1回答时，都会找不到 answer_num_block，
          # 通过找答案的赞同数block来判断到底有没有答案。
          # （感谢知乎用户 段晓晨 提出此问题）
          if answer_num_block is None:
              if self.soup.find('span', class_='count') is not None:
                  return 1
              else:
                  return 0
          return int(answer_num_block['data-num'])
docs: 获取问题答案数量.
  
          :return: 问题答案数量
          :rtype: int