public function renderItem($model, $key, $index)
    {
        if ($this->itemView === null) {
            $content = $key;
        } elseif (is_string($this->itemView)) {
            $content = $this->getView()->render($this->itemView, array_merge([
                'model' => $model,
                'key' => $key,
                'index' => $index,
                'widget' => $this,
            ], $this->viewParams));
        } else {
            $content = call_user_func($this->itemView, $model, $key, $index, $this);
        }
        $options = $this->itemOptions;
        $tag = ArrayHelper::remove($options, 'tag', 'div');
        if ($tag !== false) {
            $options['data-key'] = is_array($key) ? json_encode($key, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE) : (string) $key;

            return Html::tag($tag, $content, $options);
        } else {
            return $content;
        }
    }