public function viewAction($collectionId, $slug)
    {
        $collection = $this->get('sonata.classification.manager.collection')->findOneBy(['id' => $collectionId]);

        if (!$collection) {
            throw new NotFoundHttpException(sprintf('Unable to find the collection with id=%d', $collectionId));
        }

        return $this->render('SonataProductBundle:Collection:view.html.twig', [
           'collection' => $collection,
        ]);
    }