code: @Override
    public int compareTo(Comparable<?> other) {
      if (other instanceof Region) {
        Region r = (Region) other;
        if (this.start < r.start) {
          return -1;
        } else if (this.end > r.end) {
          return 1;
        } else {
          return 0;
        }
      } else if (other instanceof Long) {
        Long l = (Long) other;
        if (l > end) {
            return -1;
        } else if (l < start) {
            return 1;
        } else {
            return 0;
        }
      } else {
        throw new AssertionError();
      }
    }
docs: Order this region relative to another.