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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 _get_purecn_dx_files(paired, out):
 """Retrieve files generated by PureCN_Dx """

    out_base = "%s-dx" % utils.splitext_plus(out["rds"])[0]
    all_files = []
    for key, ext in [[("mutation_burden",), "_mutation_burden.csv"],
                     [("plot", "signatures"), "_signatures.pdf"],
                     [("signatures",), "_signatures.csv"]]:
        cur_file = "%s%s" % (out_base, ext)
        out = tz.update_in(out, key, lambda x: cur_file)
        all_files.append(os.path.basename(cur_file))
    return out_base, out, all_files