private function writeCellMerge(XMLWriter $objWriter, Cell $cell)
    {
        if (!$cell->isMergeRangeValueCell()) {
            return;
        }

        $mergeRange = Coordinate::splitRange($cell->getMergeRange());
        list($startCell, $endCell) = $mergeRange[0];
        $start = Coordinate::coordinateFromString($startCell);
        $end = Coordinate::coordinateFromString($endCell);
        $columnSpan = Coordinate::columnIndexFromString($end[0]) - Coordinate::columnIndexFromString($start[0]) + 1;
        $rowSpan = $end[1] - $start[1] + 1;

        $objWriter->writeAttribute('table:number-columns-spanned', $columnSpan);
        $objWriter->writeAttribute('table:number-rows-spanned', $rowSpan);
    }