def split_train_test(data, test_data_size: int):
    """Splits data into train and test.

    Args:
        data: All data.
        test_data_size: Size of the `test` data.
                        Size of the `train` will be `len(data) - test_data_size`.
    """
    train_data = data[:-test_data_size]
    test_data = data[-test_data_size:]

    return train_data, test_data