export as excel
    wb:
    output:
    fn: file name

def export_xlsx(wb, output, fn):
    """
    export as excel
    wb:
    output:
    fn: file name
    """
    wb.close()
    output.seek(0)
    response = HttpResponse(output.read(), content_type="application/vnd.ms-excel")
    cd = codecs.encode('attachment;filename=%s' % fn, 'utf-8')
    response['Content-Disposition'] = cd
    return response