code: def next_day_low_limit(self):
          "明日跌停价"
          return self.groupby(level=1).close.apply(lambda x: round((x + 0.0002)*0.9, 2)).sort_index(f next_day_low_limit(self):
          "明日跌停价"
          return self.groupby(level=1).close.apply(lambda x: round((x + 0.0002)*0.9, 2)).sort_index()
docs: 明日跌停价