static MultiMap mapLike mapMultiMapValues_precise(O func, MultiMap mm) {
  MultiMap m = similarEmptyMultiMap(mm);
  for (O key : keys(mm))
    for (O value : mm.get(key))
      m.put(key, callF_precise(func, value));
  ret m;
}

static MultiMap mapMultiMapValues_precise(MultiMap mm, O func) {
  ret mapMultiMapValues_precise(func, mm);
}

static <A, B, C> MultiMap<A, C> mapMultiMapValues_precise(IF1<B, C> func, MultiMap<A, B> mm) {
  ret mapMultiMapValues_precise((O) func, mm);
}

Began life as a copy of #1020213