Convenience function that loads two parameter sets from a rho.dat
        file, as used by CRMod for forward resistivity/phase models.

        Parameters
        ----------
        filename: string, file path
            filename of rho.dat file

        Returns
        -------
        cid_mag: int
            ID of magnitude parameter set
        cid_phase: int
            ID of phase parameter set

def load_from_rho_file(self, filename):
        """Convenience function that loads two parameter sets from a rho.dat
        file, as used by CRMod for forward resistivity/phase models.

        Parameters
        ----------
        filename: string, file path
            filename of rho.dat file

        Returns
        -------
        cid_mag: int
            ID of magnitude parameter set
        cid_phase: int
            ID of phase parameter set

        """
        data = np.loadtxt(filename, skiprows=1)
        cid_mag = self.add_data(data[:, 0])
        cid_pha = self.add_data(data[:, 1])
        return cid_mag, cid_pha