code: def max_dropback(self):
          
          return round(
              float(
                  max(
                      [
                          (self.assets.iloc[idx] - self.assets.iloc[idx::].min())
                          / self.assets.iloc[idx]
                          for idx in range(len(self.assets))
                      ]
                  )
              ),
              2
          )
docs: 最大回撤