public function registerLinkTag($options, $key = null)
    {
        if ($key === null) {
            $this->linkTags[] = $this->renderWrapperTag(Html::tag('link', '', $options), $options);
        } else {
            $this->linkTags[$key] = $this->renderWrapperTag(Html::tag('link', '', $options), $options);
        }
    }