code: public function onPreDelete(ResourceEventInterface $event)
      {
          $item = $this->getSupplierOrderItemFromEvent($event);
  
          $this->assertDeletable($item);
  
          // Initializes the supplier order's items collection before item removal.
          $item->getOrder()->getItems();
      }
docs: Pre delete event handler.
  
  @param ResourceEventInterface $event