main_engine = MainEngine()
ctp_setting = load_json("connect_ctp.json")
main_engine.add_gateway(CtpGateway)
main_engine.connect(ctp_setting, "CTP")
account_gateway = main_engine.get_gateway("CTP")
trade_records = account_gateway.query_contract_delivery()
请问大神们为什么trade_records 返回的是None