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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 delayed_bam_merge(data):
 """Perform a merge on previously prepped files, delayed in processing. Handles merging of associated split read and discordant files if present. """

    if data.get("combine"):
        assert len(data["combine"].keys()) == 1
        file_key = list(data["combine"].keys())[0]
        extras = []
        for x in data["combine"][file_key].get("extras", []):
            if isinstance(x, (list, tuple)):
                extras.extend(x)
            else:
                extras.append(x)
        if file_key in data:
            extras.append(data[file_key])
        in_files = sorted(list(set(extras)))
        out_file = tz.get_in(["combine", file_key, "out"], data, _merge_out_from_infiles(in_files))
        sup_exts = data.get(file_key + "_plus", {}).keys()
        for ext in list(sup_exts) + [""]:
            merged_file = None
            if os.path.exists(utils.append_stem(out_file, "-" + ext)):
                cur_out_file, cur_in_files = out_file, []
            if ext:
                cur_in_files = list(filter(os.path.exists, (utils.append_stem(f, "-" + ext) for f in in_files)))
                cur_out_file = utils.append_stem(out_file, "-" + ext) if len(cur_in_files) > 0 else None
            else:
                cur_in_files, cur_out_file = in_files, out_file
            if cur_out_file:
                config = copy.deepcopy(data["config"])
                if len(cur_in_files) > 0:
                    merged_file = merge_bam_files(cur_in_files, os.path.dirname(cur_out_file), data,
                                                  out_file=cur_out_file)
                else:
                    assert os.path.exists(cur_out_file)
                    merged_file = cur_out_file
            if merged_file:
                if ext:
                    data[file_key + "_plus"][ext] = merged_file
                else:
                    data[file_key] = merged_file
        data.pop("region", None)
        data.pop("combine", None)
    return [[data]]