Supplier/EventListener/SupplierDeliveryItemListener.php
public function onPreDelete(ResourceEventInterface $event)
    {
        $item = $this->getSupplierDeliveryItemFromEvent($event);

        $this->assertDeletable($item);

        // Initialize the supplier deliveries's items collection before the item removal.
        if (null !== $delivery = $item->getDelivery()) {
            $delivery->getItems();
        }
    }
public function onPreDelete(ResourceEventInterface $event)
    {
        $item = $this->getSupplierDeliveryItemFromEvent($event);

        $this->assertDeletable($item);

        // Initialize the supplier deliveries's items collection before the item removal.
        if (null !== $delivery = $item->getDelivery()) {
            $delivery->getItems();
        }
    }
Pre delete event handler.

@param ResourceEventInterface $event