def METHOD_NAME(data_already_sequential,
                                                dtype):
    if data_already_sequential:
        ar = np.array([1, 3, 0, 2, 5, 4], dtype=dtype)
    else:
        ar = np.array([1, 1, 5, 5, 8, 99, 42, 0], dtype=dtype)
    assert all(a.dtype == dtype for a in relabel_sequential(ar))