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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 postprocess_alignment(data):
 """Perform post-processing steps required on full BAM files. Prepares list of callable genome regions allowing subsequent parallelization. """

    data = cwlutils.normalize_missing(utils.to_single_data(data))
    data = cwlutils.unpack_tarballs(data, data)
    bam_file = data.get("align_bam") or data.get("work_bam")
    ref_file = dd.get_ref_file(data)
    if vmulti.bam_needs_processing(data) and bam_file and bam_file.endswith(".bam"):
        out_dir = utils.safe_makedir(os.path.join(dd.get_work_dir(data), "align",
                                                  dd.get_sample_name(data)))
        bam_file_ready = os.path.join(out_dir, os.path.basename(bam_file))
        if not utils.file_exists(bam_file_ready):
            utils.symlink_plus(bam_file, bam_file_ready)
        bam.index(bam_file_ready, data["config"])
        covinfo = callable.sample_callable_bed(bam_file_ready, ref_file, data)
        callable_region_bed, nblock_bed = \
            callable.block_regions(covinfo.raw_callable, bam_file_ready, ref_file, data)
        data["regions"] = {"nblock": nblock_bed,
                           "callable": covinfo.raw_callable,
                           "sample_callable": covinfo.callable,
                           "mapped_stats": readstats.get_cache_file(data)}
        data["depth"] = covinfo.depth_files
        data = coverage.assign_interval(data)
        data = samtools.run_and_save(data)
        data = recalibrate.prep_recal(data)
        data = recalibrate.apply_recal(data)
    elif dd.get_variant_regions(data):
        callable_region_bed, nblock_bed = \
            callable.block_regions(dd.get_variant_regions(data), bam_file, ref_file, data)
        data["regions"] = {"nblock": nblock_bed, "callable": dd.get_variant_regions(data),
                           "sample_callable": dd.get_variant_regions(data)}
    return [[data]]