public function refund(Customweb_Payment_Authorization_ITransaction $transaction)
 {
     if (!$transaction instanceof Customweb_Saferpay_Authorization_Transaction) {
         throw new Exception("The given transaction is not instanceof Customweb_Saferpay_Authorization_Transaction.");
     }
     $items = $transaction->getNonRefundedLineItems();
     return $this->partialRefund($transaction, $items, true);
 }