protected function _renderChildren(ItemInterface $item, array $options)
    {
        if ($options['depth'] !== null) {
            $options['depth'] = $options['depth'] - 1;
        }

        if ($options['matchingDepth'] !== null &&
            $options['matchingDepth'] > 0
        ) {
            $options['matchingDepth'] = $options['matchingDepth'] - 1;
        }

        $children = [];
        foreach ($item->getChildren() as $child) {
            $children[] = $this->_renderItem($child, $options);
        }

        return $children;
    }