code: def buy(self, price, volume, symbol, order_type=ft.OrderType.NORMAL, adjust_limit=0, acc_id=0):
          
          ret, data = self._trade_ctx.place_order(price=price, qty=volume, code=symbol, trd_side=ft.TrdSide.BUY,
                                                  order_type=order_type, adjust_limit=adjust_limit,
                                                  trd_env=self._env_type, acc_id=acc_id)
          if ret != ft.RET_OK:
              return ret, data
  
          order_id = 0
          for ix, row in data.iterrows():
              order_id = str(row['order_id'])
  
          return ret, order_id
docs: 买入