protected function addNature(array &$line)
    {
        if (empty($line[Tag::Nature])) {
            $shopSettings = $this->config->getShopSettings();
            switch ($shopSettings['nature_shop']) {
                case PluginConfig::Nature_Products:
                    $line[Tag::Nature] = Api::Nature_Product;
                    break;
                case PluginConfig::Nature_Services:
                    $line[Tag::Nature] = Api::Nature_Service;
                    break;
                default:
                    $invoiceSettings = $this->config->getInvoiceSettings();
                    $this->addTokenDefault($line, Tag::Nature, $invoiceSettings['nature']);
                    break;
            }
        }
    }