public function items()
    {
        $sessionId = $this->getSessionId();
        $userId = $this->auth->id();
        $items = $this->cartItem->getWithBuilder($this->instance, $this->getSessionId(), $userId)->get();

        return $items->filter(function ($item) {
            // Remove CartItem if product not exists
            if (empty($item->product)) {
                $item->delete();

                return false;
            }

            return true;
        });
    }