代码中下，感觉应该是没有错的，但是接口总是返回说没有传对应的参数：

function main() {
exchange.IO("base", "https://api.btcgateway.pro")
//var obj = {"contract_code":"TRX-USDT","volume":10000,"direction":"sell","offset":"open","lever_rate":3,"order_price_type":"optimal_5"}
var obj = {"contract_code":"TRX-USDT"}
var str = JSON.stringify(obj)
Log(obj)
Log(str)
var hy_order_id = exchange.IO("api","POST", "/linear-swap-api/v1/swap_order_info", "", str)
Log(hy_order_id)
return hy_order_id
}

调用后返回的包如下
{"ts":1619326307135,"status":"error","err_code":1066,"err_msg":"The contractCode field cannot be empty. Please re-enter."}

说我没传contract_code，实际上我传了啊