code: def amplitude(self):
          '返回DataStruct.price的百分比变化'
          res = self.price.groupby(
              level=1
          ).apply(lambda x: (x.max() - x.min()) / x.min())
          res.name = 'amplitude'
          return ref amplitude(self):
          '返回DataStruct.price的百分比变化'
          res = self.price.groupby(
              level=1
          ).apply(lambda x: (x.max() - x.min()) / x.min())
          res.name = 'amplitude'
          return res
docs: 返回DataStruct.price的百分比变化