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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 _merge_align_bams(data):
 """Merge multiple alignment BAMs, including split and discordant reads. """

    for key in (["work_bam"], ["work_bam_plus", "disc"], ["work_bam_plus", "sr"], ["umi_bam"]):
        in_files = tz.get_in(key, data, [])
        if not isinstance(in_files, (list, tuple)):
            in_files = [in_files]
        in_files = [x for x in in_files if x and x != "None"]
        if in_files:
            ext = "-%s" % key[-1] if len(key) > 1 else ""
            out_file = os.path.join(dd.get_work_dir(data), "align", dd.get_sample_name(data),
                                    "%s-sort%s.bam" % (dd.get_sample_name(data), ext))
            merged_file = merge_bam_files(in_files, utils.safe_makedir(os.path.dirname(out_file)),
                                          data, out_file=out_file)
            data = tz.update_in(data, key, lambda x: merged_file)
        else:
            data = tz.update_in(data, key, lambda x: None)
    if "align_bam" in data and "work_bam" in data:
        data["align_bam"] = data["work_bam"]
    return data