protected function setRelatedCartItem($product, $cartItemId)
    {
        $cartItemIdList = $this->facade->getRequest()->getSession()->get(
            $this->getSessionVarName(),
            array()
        );

        if (! \is_array($cartItemIdList)) {
            $cartItemIdList = array();
        }

        $cartItemIdList[$product->getId()] = $cartItemId;

        $this->facade->getRequest()->getSession()->set(
            $this->getSessionVarName(),
            $cartItemIdList
        );
    }