For a given model, return a tdMan instance

        Parameters
        ----------
        m : ndarray
            Model parameters (linear, ohm m)

def _get_tdm(self, m):
        """For a given model, return a tdMan instance

        Parameters
        ----------
        m : ndarray
            Model parameters (linear, ohm m)
        """
        m = np.atleast_2d(m)
        assert len(m.shape) == 2
        tdm = crtomo.tdMan(grid=self.grid, tempdir=self.tempdir)
        tdm.configs.add_to_configs(self.configs)

        pid_mag = tdm.parman.add_data(m[0, :])
        tdm.register_magnitude_model(pid_mag)
        if m.shape[0] == 2:
            pid_pha = tdm.parman.add_data(m[1, :])
        else:
            pid_pha = tdm.parman.add_data(np.zeros(m.shape[1]))
        tdm.register_phase_model(pid_pha)
        return tdm