private function renderHiddenInputs()
    {
        $items = $this->form->field($this->cartForm, 'productId')
            ->hiddenInput(['value' => $this->product->id])
            ->label(false);
        $items .= $this->form->field($this->cartForm, 'count')
            ->hiddenInput(['value' => self::DEFAULT_PRODUCT_COUNT])
            ->label(false);

        return $items;
    }