code: 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);
      }
docs: Initialize all default listeners