```py
            split = (
                    datasets.Split.TRAIN.subsplit(datasets.percent[:25]) +
                    datasets.Split.TEST.subsplit(datasets.percent[:50])
            )
            split = (datasets.Split.TRAIN + datasets.Split.TEST).subsplit(datasets.percent[:50])
            ```

        But this is not valid:

            ```py
            train = datasets.Split.TRAIN
            test = datasets.Split.TEST
            split = train.subsplit(datasets.percent[:25]).subsplit(datasets.percent[:25])
            split = (train.subsplit(datasets.percent[:25]) + test).subsplit(datasets.percent[:50])
            ```
    """