protected function saveItems()
    {
        $items = [];
        foreach ($this->items as $name => $item) {
            /* @var $item Item */
            $items[$name] = array_filter(
                [
                    'type' => $item->type,
                    'description' => $item->description,
                    'ruleName' => $item->ruleName,
                    'data' => $item->data,
                ]
            );
            if (isset($this->children[$name])) {
                foreach ($this->children[$name] as $child) {
                    /* @var $child Item */
                    $items[$name]['children'][] = $child->name;
                }
            }
        }
        $this->saveToFile($items, $this->itemFile);
    }