code: public DirectoryStream<Path> newDirectoryStream(
        JimfsPath dir,
        DirectoryStream.Filter<? super Path> filter,
        Set<? super LinkOption> options,
        JimfsPath basePathForStream)
        throws IOException {
      Directory file = (Directory) lookUpWithLock(dir, options).requireDirectory(dir).file();
      FileSystemView view = new FileSystemView(store, file, basePathForStream);
      JimfsSecureDirectoryStream stream = new JimfsSecureDirectoryStream(view, filter, state());
      return store.supportsFeature(Feature.SECURE_DIRECTORY_STREAM)
          ? stream
          : new DowngradedDirectoryStream(stream);
    }
docs: Creates a new directory stream for the directory located by the given path. The given {@code
  basePathForStream} is that base path that the returned stream will use. This will be the same
  as {@code dir} except for streams created relative to another secure stream.