def to_rec_single(samples, default_keys=None):
    """Convert output into a list of single CWL records.
    """
    out = []
    for data in samples:
        recs = samples_to_records([normalize_missing(utils.to_single_data(data))], default_keys)
        assert len(recs) == 1
        out.append(recs[0])
    return out