static <A, B> Map<A, B> filterByValue(Map<A, B> map, B value) {
  Map<A, B> m2 = similarEmptyMap(map);
  for (A key : keys(map)) {
    B b = map.get(key);
    if (eq(b, value))
      m2.put(key, b);
  }
  ret m2;
}

static <A, B> Map<A, B> lambdaMapLike filterByValue(IPred<B> pred, Map<A, B> map) {
  ret filterByValuePredicate(pred, map);
}