code: def plus_mons(self, month):
          
          result = []
          exist_mons = self.__get_mons
          oldraw = list(self.__raw_data)
          for i in range(month):
              nowdatetime = datetime.today() - relativedelta(months=exist_mons) -\
                            relativedelta(months=i)
              tolist = self.to_list(self.fetch_data(self.__info[0], nowdatetime))
              result = list(tolist) + result
          result = result + oldraw
          self.__get_mons = exist_mons + month
          return tuple(result)
docs: 增加 n 個月的資料
  
              :param int month: 增加 n 個月的資料
              :rtype: tuple