Return the ``<c:yVal>`` element for this series as an oxml element.
        This element contains the Y values for this series.

def yVal(self):
        """
        Return the ``<c:yVal>`` element for this series as an oxml element.
        This element contains the Y values for this series.
        """
        xml = self._yVal_tmpl.format(**{
            'nsdecls':    ' %s' % nsdecls('c'),
            'numRef_xml': self.numRef_xml(
                self._series.y_values_ref, self._series.number_format,
                self._series.y_values
            ),
        })
        return parse_xml(xml)