public function save($file, $excelWriterType = 'Excel2007')
    {
        if (!$this->phpexcel instanceof \PHPExcel) {
            throw new HtmlPhpExcelException('You must run process() first to create a phpexcel instance');
        }

        $writer = \PHPExcel_IOFactory::createWriter($this->phpexcel, $excelWriterType);
        $writer->save($file);

        return $this;
    }