code: def top_i_answer(self, i):
          
          for j, a in enumerate(self.answers):
              if j == i - 1:
                  return a
docs: 获取排名某一位的答案.
  
          :param int i: 要获取的答案的排名
          :return: 答案对象，能直接获取的属性参见answers方法
          :rtype: Answer