protected function getTemplateFilename()
    {
        $filename = $this->name . '/layout.' . $this->extension . '.twig';

        $template_path = $this->path . DIRECTORY_SEPARATOR . $filename;
        if (!file_exists($template_path)) {
            throw new \DomainException('Template file "' . $template_path . '" could not be found');
        }

        return $filename;
    }