public static function get_instance()
 {
     if (!isset(self::$instance)) {
         self::$instance = new OrderedTables_AdminCRUDManager();
     }
     return self::$instance;
 }
 public static function make_content_for_action_td($action_name, $identifiers)
 {
     $acm = OrderedTables_AdminCRUDManager::get_instance();
     return $acm->make_content_for_action_td($action_name, $identifiers);
 }