protected function addFlashMessage(FlashMessage $flashMessage)
    {
        if (!($this->flashMessageService instanceof FlashMessageService)) {
            $this->flashMessageService = GeneralUtility::makeInstance(FlashMessageService::class);
        }
        /** @var $defaultFlashMessageQueue \TYPO3\CMS\Core\Messaging\FlashMessageQueue */
        $defaultFlashMessageQueue = $this->flashMessageService->getMessageQueueByIdentifier();
        $defaultFlashMessageQueue->enqueue($flashMessage);
    }