/**
  * Get SEO score for post from WordPress SEO Plugin
  *
  * @param int $post_id
  *
  * @return string
  */
 protected function get_wp_seo_score($post_id)
 {
     // Get seo score from WordPress SEO
     $score = WPSEO_Metabox::get_value('linkdex', $post_id);
     if ($score !== '') {
         $nr = $this->wpseo_calc($score, '/', 10, true);
         $score_label = $this->wpseo_translate_score($nr);
         unset($nr);
     } else {
         $score_label = 'na';
     }
     return $score_label;
 }