def cancelOrder(self, order):
        """撤单"""
        ins_dict = self.gateway.get_ins_dict(order.order_book_id)
        if ins_dict is None:
            return None

        self.req_id += 1
        req = {
            'InstrumentID': ins_dict.instrument_id,
            'ExchangeID': ins_dict.exchange_id,
            'OrderRef': str(order.order_id),
            'FrontID': int(self.front_id),
            'SessionID': int(self.session_id),

            'ActionFlag': defineDict['THOST_FTDC_AF_Delete'],
            'BrokerID': self.broker_id,
            'InvestorID': self.user_id,
        }

        self.reqOrderAction(req, self.req_id)
        return self.req_id