public function findCartItem(CartEvent $event)
    {
        // Do not try to find a cartItem if one exists in the event, as previous event handlers
        // mays have put it in th event.
        if (null === $event->getCartItem() && null !== $foundItem = CartItemQuery::create()
            ->filterByCartId($event->getCart()->getId())
            ->filterByProductId($event->getProduct())
            ->filterByProductSaleElementsId($event->getProductSaleElementsId())
            ->findOne()) {
            $event->setCartItem($foundItem);
        }
    }