def METHOD_NAME():
    @quantity_to_dataclass(eph=('rh', sbd.Ephem), orbit=('a', sbd.Orbit))
    def contrived(eph, orbit):
        return (eph['rh'] / orbit['a']).decompose()
    rh = 1 * u.au
    a = 2 * u.au
    assert np.isclose(contrived(rh, a).value, 0.5)
    with pytest.raises(FieldError):
        contrived(1, a)
    with pytest.raises(FieldError):
        contrived(rh, 2 * u.s)