code: @Override
    public int compareTo(Annotation note) {
      return start_time > note.start_time ? 1 : 
        start_time < note.start_time ? -1 : 0;
    }
docs: Compares the {@code #start_time} of this annotation to the given note
  @return 1 if the local start time is greater, -1 if it's less or 0 if
  equal