private function getXmlString(array $fields = []): string
    {
        $xmlData = [];
        $xmlData[] = '<Row>';
        foreach ($fields as $key => $value) {
            $value = htmlspecialchars($value);

            $value = str_replace(["\r\n", "\r", "\n"], '&#10;', $value);
            $dataType = 'String';
            if (0 !== $this->position || !$this->showHeaders) {
                $dataType = $this->getDataType((string) $key, $value);
            }
            $xmlData[] = '<Cell><Data ss:Type="'.$dataType.'">'.$value.'</Data></Cell>';
        }
        $xmlData[] = '</Row>';

        return implode('', $xmlData);
    }