insert_order的limit_price

请教：上面是代码，下面是控制台输出。为什么写的5000，输出是个nan？代码：

order = api.insert_order(symbol=SYMBOL, direction="SELL", offset="CLOSE", volume=1, limit_price=5000)
    print(order)

输出：{‘order_id’: ‘257a74de0fe8c623ac4683bbd83704db’, ‘exchange_order_id’: ”, ‘exchange_id’: ‘SHFE’, ‘instrument_id’: ‘rb2001’, ‘direction’: ‘SELL’, ‘offset’: ‘CLOSE’, ‘volume_orign’: 1, ‘volume_left’: 1, ‘limit_price’: nan, ‘price_type’: ”, ‘volume_condition’: ”, ‘time_condition’: ”, ‘insert_date_time’: 0, ‘last_msg’: ”, ‘status’: ‘ALIVE’}