code: def _flatten_plus_safe(data_and_files):
      
      data, rollback_files = _normalize_args(data_and_files)
      with tx_tmpdir(data) as tmpdir:
          tx_files = [os.path.join(tmpdir, os.path.basename(f))
                      for f in rollback_files]
          yield tx_files, rollback_files
docs: Flatten names of files and create temporary file names.