code: def tx(self):
          
          xml = self._tx_tmpl.format(**{
              'wksht_ref':   self._series.name_ref,
              'series_name': self.name,
              'nsdecls':     ' %s' % nsdecls('c'),
          })
          return parse_xml(xml)
docs: Return a ``<c:tx>`` oxml element for this series, containing the
          series name.