def train_test_split(data, test_len):
    """
    Train/ Test split
    :param data: (np.array) Sequence to split
    :param test_len: (int) length of test sequence
    :return: np.array, np.array: train sequence, test sequence
    """
    # print("[DataProcessor] Train/Test split")
    if test_len == 0:
        return data, None
    return data[:-test_len], data[-test_len:]