def test_shared_times_bounds_empty_input(self):
        """
        Tests that `get_shared_times_bounds` returns `None` when
        handed a non-`None` input that has no timesteps.
        """
        series = linear_timeseries(start=0, length=0, freq=1)
        assert get_shared_times_bounds(series) is None
        assert get_shared_times_bounds(series.time_index) is None
        assert get_shared_times_bounds(series, series.time_index) is None

        Tests that `get_shared_times_bounds` returns `None` when
        handed a non-`None` input that has no timesteps.
        
darts/tests/utils/tabularization/test_get_shared_times_bounds.py