code: def create_unique_autosave_filename(self, filename, autosave_dir):
          
          basename = osp.basename(filename)
          autosave_filename = osp.join(autosave_dir, basename)
          if autosave_filename in self.name_mapping.values():
              counter = 0
              root, ext = osp.splitext(basename)
              while autosave_filename in self.name_mapping.values():
                  counter += 1
                  autosave_basename = '{}-{}{}'.format(root, counter, ext)
                  autosave_filename = osp.join(autosave_dir, autosave_basename)
          return autosave_filename
docs: Create unique autosave file name for specified file name.
  
          Args:
              filename (str): original file name
              autosave_dir (str): directory in which autosave files are stored