private function writeDataLabels(XMLWriter $objWriter, Layout $chartLayout = null)
    {
        $objWriter->startElement('c:dLbls');

        $objWriter->startElement('c:showLegendKey');
        $showLegendKey = (empty($chartLayout)) ? 0 : $chartLayout->getShowLegendKey();
        $objWriter->writeAttribute('val', ((empty($showLegendKey)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->startElement('c:showVal');
        $showVal = (empty($chartLayout)) ? 0 : $chartLayout->getShowVal();
        $objWriter->writeAttribute('val', ((empty($showVal)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->startElement('c:showCatName');
        $showCatName = (empty($chartLayout)) ? 0 : $chartLayout->getShowCatName();
        $objWriter->writeAttribute('val', ((empty($showCatName)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->startElement('c:showSerName');
        $showSerName = (empty($chartLayout)) ? 0 : $chartLayout->getShowSerName();
        $objWriter->writeAttribute('val', ((empty($showSerName)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->startElement('c:showPercent');
        $showPercent = (empty($chartLayout)) ? 0 : $chartLayout->getShowPercent();
        $objWriter->writeAttribute('val', ((empty($showPercent)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->startElement('c:showBubbleSize');
        $showBubbleSize = (empty($chartLayout)) ? 0 : $chartLayout->getShowBubbleSize();
        $objWriter->writeAttribute('val', ((empty($showBubbleSize)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->startElement('c:showLeaderLines');
        $showLeaderLines = (empty($chartLayout)) ? 1 : $chartLayout->getShowLeaderLines();
        $objWriter->writeAttribute('val', ((empty($showLeaderLines)) ? 0 : 1));
        $objWriter->endElement();

        $objWriter->endElement();
    }