code: def mean_values(self):
          
          if not self.istransformed:
              return self.pst.parameter_data.parval1.copy()
          else:
              # vals = (self.pst.parameter_data.parval1 *
              #         self.pst.parameter_data.scale) +\
              #         self.pst.parameter_data.offset
              vals = self.pst.parameter_data.parval1.copy()
              vals[self.log_indexer] = np.log10(vals[self.log_indexer])
              return vals
docs: the mean value vector while respecting log transform
  
          Returns
          -------
          mean_values : pandas.Series