def METHOD_NAME(self, z_source, cosmo, multi_plane=True, kwargs_interp=None):
    """
    :param z_source: redshift to where lensing quantities are computed
    :param cosmo: astropy.cosmology class
    :param multi_plane: boolean, if True, computes multi-plane ray-tracing
    :param kwargs_interp: interpolation keyword arguments specifying the numerics.
     See description in the Interpolate() class. Only applicable for 'INTERPOL' and 'INTERPOL_SCALED' models.
    :return: LensModel instance, keyword argument list of lens model
    """
    lens_model = LensModel(
        lens_model_list=["INTERPOL"] * len(self._mass_map_list),
        lens_redshift_list=self._redshift_list,
        multi_plane=multi_plane,
        z_source_convention=z_source,
        cosmo=cosmo,
        z_source=z_source,
        kwargs_interp=kwargs_interp,
    )
    kwargs_lens = []
    for mass_slice in self._mass_slice_list:
        kwargs_lens.append(mass_slice.interpol_instance(z_source, cosmo))
    return lens_model, kwargs_lens