private function findMatchingShipmentItem(InvoiceLineInterface $line, ShipmentInterface $shipment)
    {
        $saleItem = $line->getSaleItem();

        foreach ($shipment->getItems() as $shipmentItem) {
            if ($saleItem === $shipmentItem->getSaleItem()) {
                return $shipmentItem;
            }
        }

        return null;
    }