protected function _initialize_event_listeners()
    {
        foreach($this->event_listeners as $event_listener => $e)
        {
            if(isset($this->$event_listener) && !empty($this->$event_listener)){
                foreach($this->$event_listener as $event){
                    $this->subscribe($event_listener, $event);
                }
            }
        }

        $this->subscribe('before_update', 'protect_attributes', TRUE);
    }