code: DirectoryEntry lookUp(File workingDirectory, JimfsPath path, Set<? super LinkOption> options)
        throws IOException {
      state.checkOpen();
      return tree.lookUp(workingDirectory, path, options);
    }
docs: Looks up the file at the given path using the given link options. If the path is relative, the
  lookup is relative to the given working directory.
  
  @throws NoSuchFileException if an element of the path other than the final element does not
  resolve to a directory or symbolic link (e.g. it doesn't exist or is a regular file)
  @throws IOException if a symbolic link cycle is detected or the depth of symbolic link
  recursion otherwise exceeds a threshold