Get the names of adjustable parameters in the ParameterEnsemble

        Returns
        -------
        list : list
            adjustable parameter names

def adj_names(self):
        """ Get the names of adjustable parameters in the ParameterEnsemble

        Returns
        -------
        list : list
            adjustable parameter names

        """
        return list(self.pst.parameter_data.parnme.loc[~self.fixed_indexer])