'Check models give different answers, yet are close.'

@pytest.mark.parametrize('kind', ('mean', 'apparent'))
def test_model_uniqueness(self, kind):

    for (model1, model2) in itertools.combinations(SIDEREAL_TIME_MODELS[kind].keys(), 2):
        gst1 = self.t.sidereal_time(kind, 'greenwich', model1)
        gst2 = self.t.sidereal_time(kind, 'greenwich', model2)
        assert np.all((gst1.value != gst2.value))
        assert within_1_second(gst1.value, gst2.value)
        lst1 = self.t.sidereal_time(kind, None, model1)
        lst2 = self.t.sidereal_time(kind, None, model2)
        assert np.all((lst1.value != lst2.value))
        assert within_1_second(lst1.value, lst2.value)
