public function ship($purchaseOrderId, $order)
    {
        if(!is_numeric($purchaseOrderId)){
            throw new \Exception("purchaseOrderId must be numeric",1448480750);
        }

        $schema = [
            '/orderShipment' => [
                'namespace' => 'ns3',
                'childNamespace' => 'ns3',
            ],
            '/orderShipment/orderLines' => [
                'sendItemsAs' => 'orderLine',
            ],
            '/orderShipment/orderLines/orderLine/orderLineStatuses' => [
                'sendItemsAs' => 'orderLineStatus',
            ],
            '@namespaces' => [
                'ns3' => 'http://walmart.com/mp/v3/orders'
            ],
        ];

        $a2x = new A2X($order, $schema);
        $xml = $a2x->asXml();

        return $this->shipOrder([
            'purchaseOrderId' => $purchaseOrderId,
            'order' => $xml,
        ]);
    }