def test_input_transformed_multiple_samples(self):
        """
        Tests that `stack_samples` and `unstack_samples` correctly
        implemented when considering multi-sample timeseries.
        """
        test_input = constant_timeseries(value=1, length=10)
        test_input = test_input.concatenate(
            constant_timeseries(value=2, length=10), axis="sample"
        )

        mock = self.DataTransformerMock(scale=2, translation=10, stack_samples=True)
        transformed = mock.transform(test_input)

        # 2 * 1 + 10 = 12
        expected = constant_timeseries(value=12, length=10)
        # 2 * 2 + 10 = 14
        expected = expected.concatenate(
            constant_timeseries(value=14, length=10), axis="sample"
        )
        assert transformed == expected
        # Should get input back:
        inv = mock.inverse_transform(transformed)
        assert inv == test_input

        Tests that `stack_samples` and `unstack_samples` correctly
        implemented when considering multi-sample timeseries.
        
darts/tests/dataprocessing/transformers/test_invertible_data_transformer.py