Sample of preparing and rendering

PartletHandler.php

        $this->preparer->prepare($partlet);

        $content = $this->render($partlet);

        if (is_array($content)) {
            return new JsonResponse($content);
        } else {
            $containerClass = $partlet->getContainerPartlet();
            $containerWidget = $this->dic->getInstanceOfClass($containerClass);
            $this->preparer->prepare($containerWidget, ['content' => $content]);
            $content = $this->render($containerWidget);

            return new Response($content);
        }