def test_shared_times_empty_input(self):
        """
        Tests that `get_shared_times` returns `None` when
        given a non-`None` input with no timesteps.
        """
        series = linear_timeseries(start=0, length=0, freq=1)
        assert get_shared_times(series) is None
        assert get_shared_times(series.time_index) is None
        assert get_shared_times(series, series.time_index) is None

        Tests that `get_shared_times` returns `None` when
        given a non-`None` input with no timesteps.
        
darts/tests/utils/tabularization/test_get_shared_times.py