Vererbungsfrage im Filter

Shopware 5 Plugins
1

Wie kann ich bei $eventArgs->get(‘subject’)->_template->fetch() im Filter Shopware_Components_Document_Render_FilterHtml die Vererbung zum Theme einbauen ?
Die normalen Wege habe ich schon versucht.

namespace WebvQuotationRequirementRequest\Subscriber;

use Enlight\Event\SubscriberInterface;

class Document implements SubscriberInterface
{

    public static function getSubscribedEvents()
    {
        return [
            'Shopware_Components_Document_Render_FilterHtml' => 'onFilterMpdfConfig',
        ];
    }

    public function onFilterMpdfConfig(\Enlight_Event_EventArgs $eventArgs)
    {

        $returnData = $eventArgs->getReturn();

        $action = $eventArgs->get('subject');
        if (strpos($action->_renderer, 'WebvQuotationRequirementRequestPdf') !== false) {
            $renderArgs = explode(':', $action->_renderer, 2);

            if (isset($renderArgs[1])) {
                $data = unserialize(base64_decode($renderArgs[1]));
                $action->_view->assign('RenderData', $data);
            }

            $action->_renderer = 'pdf';


            $returnData = $action->_template->fetch('documents/WebvQuotationRequirementRequestPdf.tpl', $action->_view);
        }


        return $returnData;
    }

}