code: public static int compare(CharSequence s1, CharSequence s2, IntUnaryOperator op)
      {
          return Streams.compare(s1.codePoints().map(op), s2.codePoints().map(op));
      }
docs: Compares two CharSequences with codepoint mapping
  @param s1
  @param s2
  @param op Codepoint mapping before comparison.
  @return