protected function getItemsCode(): string
    {
        $code = '';
        if ($this->countItems() > 0) {
            foreach ($this->getAllItems() as $item) {
                if (is_string($item)) {
                    $code .= $item;
                } else {
                    $code .= (string) $item;
                }
            }
        }
        return $code;
    }