public function writeVMLComments(\PhpOffice\PhpSpreadsheet\Worksheet\Worksheet $pWorksheet)
    {
        // Create XML writer
        $objWriter = null;
        if ($this->getParentWriter()->getUseDiskCaching()) {
            $objWriter = new XMLWriter(XMLWriter::STORAGE_DISK, $this->getParentWriter()->getDiskCachingDirectory());
        } else {
            $objWriter = new XMLWriter(XMLWriter::STORAGE_MEMORY);
        }

        // XML header
        $objWriter->startDocument('1.0', 'UTF-8', 'yes');

        // Comments cache
        $comments = $pWorksheet->getComments();

        // xml
        $objWriter->startElement('xml');
        $objWriter->writeAttribute('xmlns:v', 'urn:schemas-microsoft-com:vml');
        $objWriter->writeAttribute('xmlns:o', 'urn:schemas-microsoft-com:office:office');
        $objWriter->writeAttribute('xmlns:x', 'urn:schemas-microsoft-com:office:excel');

        // o:shapelayout
        $objWriter->startElement('o:shapelayout');
        $objWriter->writeAttribute('v:ext', 'edit');

        // o:idmap
        $objWriter->startElement('o:idmap');
        $objWriter->writeAttribute('v:ext', 'edit');
        $objWriter->writeAttribute('data', '1');
        $objWriter->endElement();

        $objWriter->endElement();

        // v:shapetype
        $objWriter->startElement('v:shapetype');
        $objWriter->writeAttribute('id', '_x0000_t202');
        $objWriter->writeAttribute('coordsize', '21600,21600');
        $objWriter->writeAttribute('o:spt', '202');
        $objWriter->writeAttribute('path', 'm,l,21600r21600,l21600,xe');

        // v:stroke
        $objWriter->startElement('v:stroke');
        $objWriter->writeAttribute('joinstyle', 'miter');
        $objWriter->endElement();

        // v:path
        $objWriter->startElement('v:path');
        $objWriter->writeAttribute('gradientshapeok', 't');
        $objWriter->writeAttribute('o:connecttype', 'rect');
        $objWriter->endElement();

        $objWriter->endElement();

        // Loop through comments
        foreach ($comments as $key => $value) {
            $this->writeVMLComment($objWriter, $key, $value);
        }

        $objWriter->endElement();

        // Return
        return $objWriter->getData();
    }