def METHOD_NAME(self):
    # Write the <worksheet> element. This is the root element.
    schema = 'http://schemas.openxmlformats.org/'
    xmlns = schema + 'spreadsheetml/2006/main'
    xmlns_r = schema + 'officeDocument/2006/relationships'
    attributes = [
        ('xmlns', xmlns),
        ('xmlns:r', xmlns_r)]
    self._xml_start_tag('chartsheet', attributes)