def objective_bounds(self):
        """
        Return objective bounds


        Returns
        -------
        lower : list of floats
            Lower boundaries for the objectives

        Upper : list of floats
            Upper boundaries for the objectives

        """
        if self.ideal and self.nadir:
            return self.ideal, self.nadir
        raise NotImplementedError(
            "Ideal and nadir value calculation is not yet implemented"
        )