self.levels=[1419.73, 1397.81032, 1384.24984, 1373.29, 1362.33016, 1346.72632, 1326.85]
         if self.levels is not None:
            for level in self.levels.values():
                if level is not None and level not in self.used_levels:
                    self.buy_price = level
                    print(self.buy_price)
                    self.buy(Decimal(self.buy_price), Decimal(0.2 * self.fixed_size), stop=True)
                    self.used_levels.append(level)

这段代码中，回测时，停止单的价格低于当前价格时会立即成交。要如何实现当前价格跌到指定价格的时候才买入。

用限价单