例如：
var message1 ="symbol=XBTUSD&orderQty=1&price=8000&ordType=Limit&execInst=ParticipateDoNotInitiate"
var message2 ="symbol=XBTUSD&orderQty=1&price=9000&ordType=Limit&execInst=ParticipateDoNotInitiate"
var message = [message1,message2]
exchange.IO("api","POST","/api/v1/order/bulk",message)
报错如下：
Error: bad element for argument #3[3] to 'Exchange_Futures_OP' (got object) at onTick

请问，bitmex具体的批量下单的代码格式应该怎么写？有相关例子吗？谢谢！