static <A, B> Map<A, B> filterMap(Map<A, B> map, IF2<A, B, Bool> f) {
  if (map == null) null;
  Map<A, B> m2 = similarEmptyMap(map);
  for (A a, B b : map) {
    if (f.get(a, b))
      m2.put(a, b);
  }
  ret m2;
}

static <A, B> Map<A, B> curry1Like filterMap(IF2<A, B, Bool> f, Map<A, B> map) {
  ret filterMap(map, f);
}

static <A, B> Map<A, B> filterMap(Map<A, B> map, A... keys) {
  ret getMultipleKeys(map, keys);
}



static <A, B> Map<A, B> filterMap(Map<A, B> map, Iterable<A> keys) {
  ret getMultipleKeys(map, keys);
}

Began life as a copy of #1008064