public static function rp4wp_get_related_posts_sql($sql, $post_id, $post_type) {
    global $wpdb;
    if ('post' !== $post_type) {
      return $sql;
    }
    $category_ids = [];
    $category_slugs = ['allgemein', 'ausstellung', 'beruf', 'blaulicht', 'brauchtum', 'bremen', 'bremerhaven', 'deichbrand', 'der-norden', 'eisbaeren-bremerhaven', 'europameisterschaft-2016', 'fernsehen', 'fischtown-pinguins', 'pinguins-app-premium-feed', 'pinguins-app-premium-feed-gallery', 'pinguins-app-premium-feed-only'];
    foreach ($category_slugs as $slug) {
      $category_ids[] = get_category_by_slug($slug)->term_id;
    }
    $sql_replace = sprintf("INNER JOIN " . $wpdb->term_relationships . " ON (R.`post_id` = " . $wpdb->term_relationships . ".object_id) INNER JOIN " . $wpdb->term_taxonomy . " ON (" . $wpdb->term_relationships . ".term_taxonomy_id = " . $wpdb->term_taxonomy . ".term_taxonomy_id) WHERE 1=1 AND " . $wpdb->term_taxonomy . ".taxonomy = 'category' AND " . $wpdb->term_taxonomy . ".term_id NOT IN ( %s )", " 16 ");
    return str_ireplace('WHERE 1=1', $sql_replace, $sql);
  }