public function assignCompleteCallback(GearmanTask $gearmanTask, $contextReference = null)
    {
        $event = new GearmanClientCallbackCompleteEvent($gearmanTask);
        if (!is_null($contextReference)) {
            $event->setContext($contextReference);
        }
        $this->eventDispatcher->dispatch(
            GearmanEvents::GEARMAN_CLIENT_CALLBACK_COMPLETE,
            $event
        );
    }