docs: def _get_per_data_dir(self, dir_base, subpath):
          """Extend the given base directory with a per-data component.
  
          The method creates a private path for the
          :class:`~resolwe.flow.models.Data` object, such as::
  
              ./test_data/1/
  
          if ``base_dir`` is ``'./test_data'`` and ``subpath`` is ``1``.
  
          :param dir_base: The base path to be extended. This will usually
              be one of the directories configured in the
              ``FLOW_EXECUTOR`` setting.
          :param subpath: Objects's subpath used for the extending.
          :return: The new path for the :class:`~resolwe.flow.models.Data`
              object.
          :rtype: str
          """
          # Use Django settings here, because the state must be preserved
          # across events. This also implies the directory settings can't
          # be patched outside the manager and then just sent along in the
          # command packets.
          result = self.settings_actual.get('FLOW_EXECUTOR', {}).get(dir_base, '')
          return os.path.join(result, subpath)