public function getSeoMetaTags($extension, $content)
    {
        $seo = [];
        if (array_key_exists('seo', $extension)) {
            $seo = $extension['seo'];
        }
        $excerpt = [];
        if (array_key_exists('excerpt', $extension)) {
            $excerpt = $extension['excerpt'];
        }

        // fallback for seo description
        if (
            (!array_key_exists('description', $seo) || '' === $seo['description']) &&
            array_key_exists('description', $excerpt) && '' !== $excerpt['description']
        ) {
            $seo['description'] = strip_tags($excerpt['description']);
        }

        $seo['description'] = substr($seo['description'], 0, 155);

        // generate robots content
        $robots = [];
        $robots[] = (array_key_exists('noIndex', $seo) && true === $seo['noIndex']) ? 'noIndex' : 'index';
        $robots[] = (array_key_exists('noFollow', $seo) && true === $seo['noFollow']) ? 'noFollow' : 'follow';

        // build meta tags
        $result = [];
        $result[] = $this->getMeta('description', $seo['description']);
        $result[] = $this->getMeta('keywords', $seo['keywords']);
        $result[] = $this->getMeta('robots', strtoupper(implode(', ', $robots)));

        return implode(PHP_EOL, $result);
    }