# stratified split
        >>> ds = load_dataset("imdb",split="train")
        Dataset({
            features: ['text', 'label'],
            num_rows: 25000
        })
        >>> ds = ds.train_test_split(test_size=0.2, stratify_by_column="label")
        DatasetDict({
            train: Dataset({
                features: ['text', 'label'],
                num_rows: 20000
            })
            test: Dataset({
                features: ['text', 'label'],
                num_rows: 5000
            })
        })
        ```
        """
        from .dataset_dict import DatasetDict  # import here because of circular dependency