docs: def retrieve_log_trace(self, filename=None, dir=None):
          """Retrieves the application log and trace files of the job
          and saves them as a compressed tar file.
  
          An existing file with the same name will be overwritten.
  
          Args:
              filename (str): name of the created tar file. Defaults to `job_<id>_<timestamp>.tar.gz` where `id` is the job identifier and `timestamp` is the number of seconds since the Unix epoch, for example ``job_355_1511995995.tar.gz``.
              dir (str): a valid directory in which to save the archive. Defaults to the current directory.
  
          Returns:
              str: the path to the created tar file, or ``None`` if retrieving a job's logs is not supported in the version of IBM Streams to which the job is submitted.
  
          .. versionadded:: 1.8
          """
  
          if hasattr(self, "applicationLogTrace") and self.applicationLogTrace is not None:
              logger.debug("Retrieving application logs from: " + self.applicationLogTrace)
              if not filename:
                  filename = _file_name('job', self.id, '.tar.gz')
  
              return self.rest_client._retrieve_file(self.applicationLogTrace, filename, dir, 'application/x-compressed')
          else:
              return None