static <A, B extends Number> L<A> keysWithBiggestValue(Map<A, B> map) {
  new L<A> l;
  Number bestScore = null;
  for (A key : keys(map)) {
    Number score = map.get(key);
    if (empty(l) || cmp(score, bestScore) >= 0) {
      if (nempty(l) && cmp(score, bestScore) > 0) l.clear();
      l.add(key);
      bestScore = score;
    }
  }
  ret l;
}