def METHOD_NAME(target_windows_ds):
    """Test the case where there's only one category in the metadata, e.g.
    'subject'.
    """
    n_windows = 3
    n_sequences = 10
    md = target_windows_ds.get_metadata().drop(columns=['session', 'run'])
    sampler = BalancedSequenceSampler(
        md, n_windows, n_sequences=n_sequences, random_state=87)
    seqs = [seq for seq in sampler]
    assert len(seqs) == n_sequences
    assert all([len(s) == n_windows for s in seqs])