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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 make_list_threads_message(self, py_db, seq):
 """ returns thread listing as XML """

        try:
            threads = get_non_pydevd_threads()
            cmd_text = ["<xml>"]
            append = cmd_text.append
            for thread in threads:
                if is_thread_alive(thread):
                    append(self._thread_to_xml(thread))
            append("</xml>")
            return NetCommand(CMD_RETURN, seq, ''.join(cmd_text))
        except:
            return self.make_error_message(seq, get_exception_traceback_str())