private function get_sitemap_from_cache( $type, $page_number ) {

    $this->transient = false;

    if ( $this->cache->is_enabled() !== true ) {
      return false;
    }

    
/**
 * Fires before the attempt to retrieve XML sitemap from the transient cache.
 *
 * @param WPSEO_Sitemaps $sitemaps Sitemaps object.
 */
    do_action( 'wpseo_sitemap_stylesheet_cache_' . $type, $this );

    $sitemap_cache_data = $this->cache->get_sitemap_data( $type, $page_number );

    // No cache was found, refresh it because cache is enabled.
    if ( empty( $sitemap_cache_data ) ) {
      return $this->refresh_sitemap_cache( $type, $page_number );
    }

    // Cache object was found, parse information.
    $this->transient = true;

    $this->sitemap     = $sitemap_cache_data->get_sitemap();
    $this->bad_sitemap = ! $sitemap_cache_data->is_usable();

    return true;
  }