/**
  * Fetch a value from the session data.
  *
  * @param BoltFormsCustomDataEvent $event
  */
 public function sessionValue(BoltFormsCustomDataEvent $event)
 {
     $params = $event->eventParams();
     if (!isset($params['key'])) {
         return;
     }
     $event->setData($this->app['session']->get($params['key']));
 }