@Nullable
  private static Long getLastSavedStamp(VirtualFile file) {
    Long l = file.getUserData(LAST_TS_KEY);
    if (l == null) {
      try (final DataInputStream stream = LAST_TS_ATTR.readFileAttribute(file)) {
        if (stream != null) {
          l = stream.readLong();
        }
      }
      catch (IOException e) {
        LOG.info(e);
      }
    }
    return l;
  }
@Nullable
  private static Long getLastSavedStamp(VirtualFile file)