Perform compression of output files for long term storage.

def compress(samples, run_parallel):
    """Perform compression of output files for long term storage.
    """
    to_cram = []
    finished = []
    for data in [x[0] for x in samples]:
        if "cram" in dd.get_archive(data) or "cram-lossless" in dd.get_archive(data):
            to_cram.append([data])
        else:
            finished.append([data])
    crammed = run_parallel("archive_to_cram", to_cram)
    return finished + crammed