code: private function writeBookViews(XMLWriter $objWriter, Spreadsheet $spreadsheet)
      {
          // bookViews
          $objWriter->startElement('bookViews');
  
          // workbookView
          $objWriter->startElement('workbookView');
  
          $objWriter->writeAttribute('activeTab', $spreadsheet->getActiveSheetIndex());
          $objWriter->writeAttribute('autoFilterDateGrouping', '1');
          $objWriter->writeAttribute('firstSheet', '0');
          $objWriter->writeAttribute('minimized', '0');
          $objWriter->writeAttribute('showHorizontalScroll', '1');
          $objWriter->writeAttribute('showSheetTabs', '1');
          $objWriter->writeAttribute('showVerticalScroll', '1');
          $objWriter->writeAttribute('tabRatio', '600');
          $objWriter->writeAttribute('visibility', 'visible');
  
          $objWriter->endElement();
  
          $objWriter->endElement();
      }
docs: Write BookViews.
  
  @param XMLWriter $objWriter XML Writer
  @param Spreadsheet $spreadsheet