public function generateDutyCalculatorDocuments(Varien_Event_Observer $observer)
 {
     /* @var $shipment Mage_Sales_Model_Order_Shipment */
     $shipment = $observer->getShipment();
     if ($shipment->getDcOrderId()) {
         $result = Dutycalculator_Charge_Model_Importdutytaxes::generateDocuments($shipment);
         if ($result) {
             $shipment->setCommercialInvoiceUrl($result['commercial_invoice_url']);
             $shipment->setPackingListUrl($result['packing_list_url']);
             $shipment->getResource()->save($shipment);
         }
         Dutycalculator_Charge_Model_Importdutytaxes::storeShipmentCalculation($shipment);
     }
     return $this;
 }