public function getItemWeight(): int
    {
        if ($this->itemWeight !== null) {
            return $this->itemWeight;
        }

        $this->itemWeight = 0;
        /** @var PackedItem $item */
        foreach ($this->items as $item) {
            $this->itemWeight += $item->getItem()->getWeight();
        }

        return $this->itemWeight;
    }