Convert BAM archive files into indexed CRAM.

def to_cram(data):
    """Convert BAM archive files into indexed CRAM.
    """
    data = utils.to_single_data(data)
    cram_file = cram.compress(dd.get_work_bam(data) or dd.get_align_bam(data), data)
    out_key = "archive_bam" if cwlutils.is_cwl_run(data) else "work_bam"
    data[out_key] = cram_file
    return [[data]]