/**
  * the singleton pattern
  *
  * @return Admin_Setup_DemoData
  */
 public static function getInstance()
 {
     if (self::$_instance === NULL) {
         self::$_instance = new Admin_Setup_DemoData();
     }
     return self::$_instance;
 }
 /**
  * unsets the instance to save memory, be aware that hasBeenRun still needs to work after unsetting!
  *
  */
 public function unsetInstance()
 {
     if (self::$_instance !== NULL) {
         self::$_instance = null;
     }
 }