public static function get_instance()
 {
     if (self::$_instance instanceof Agm_AdminHelp) {
         return self::$_instance;
     }
     self::$_instance = new Agm_AdminHelp();
     return self::$_instance;
 }
 private function __construct()
 {
     $this->_help = Agm_AdminHelp::get_instance();
 }