protected function _renderChildren($item, $level)
    {
        if (!$this->_hasChildren($item)) {
            return '';
        }

        $subnavItems = $this->renderNested($item['children'], $level);
        if ($subnavItems === '') {
            return '';
        }

        $templater = $this->templater();

        $htmlAttributes = [
            'class' => $this->_buildSubnavClasses($item, $level)
        ];

        return $this->formatTemplate('subnav', [
            'attrs' => $templater->formatAttributes($htmlAttributes),
            'items' => $subnavItems
        ]);
    }