code: def _format_attrs(self):
          
          attrs = super()._format_attrs()
          for attrib in self._attributes:
              if attrib == 'freq':
                  freq = self.freqstr
                  if freq is not None:
                      freq = "'%s'" % freq
                  attrs.append(('freq', freq))
          return attrs
docs: Return a list of tuples of the (attr,formatted_value).