static <A> Pair<A, PosNegScore> worstPosNegScore_keyAndValue(Map<A, PosNegScore> map) {
  new Lowest<Pair<A, PosNegScore>> best;
  if (map != null) for (A key, PosNegScore score : map) {
    best.put(pair(key, score), score.pos-score.neg);
  }
  ret best!;
}