code: def ma_bias_ratio(self, date1, date2, data):
          
          data1 = self.moving_average(data, date1)
          data2 = self.moving_average(data, date2)
          cal_list = []
          for i in range(1, min(len(data1), len(data2)) + 1):
              cal_list.append(data1[-i] - data2[-i])
          cal_list.reverse()
          return cal_list
docs: 計算乖離率（均價）
              date1 - date2
  
              :param int data1: n 日
              :param int data2: m 日
              :rtype: 序列 舊→新