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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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]]