code: def get_autosave_filename(self, filename):
          
          try:
              autosave_filename = self.name_mapping[filename]
          except KeyError:
              autosave_dir = get_conf_path('autosave')
              if not osp.isdir(autosave_dir):
                  try:
                      os.mkdir(autosave_dir)
                  except EnvironmentError as error:
                      action = _('Error while creating autosave directory')
                      msgbox = AutosaveErrorDialog(action, error)
                      msgbox.exec_if_enabled()
              autosave_filename = self.create_unique_autosave_filename(
                      filename, autosave_dir)
              self.name_mapping[filename] = autosave_filename
              self.stack.sig_option_changed.emit(
                      'autosave_mapping', self.name_mapping)
              logger.debug('New autosave file name')
          return autosave_filename
docs: Get name of autosave file for specified file name.
  
          This function uses the dict in `self.name_mapping`. If `filename` is
          in the mapping, then return the corresponding autosave file name.
          Otherwise, construct a unique file name and update the mapping.
  
          Args:
              filename (str): original file name