static <A, B> MultiSetMap<A, B> multiSetMap_innerCustomCompactTreeSet_outerTreeMap(Comparator<B> innerComparator) {
  MultiSetMap<A, B> m = new MultiSetMap<A, B>() {
    Set<B> _makeEmptySet() { ret new CompactTreeSet(innerComparator); }
  };
  m.data = new TreeMap;
  ret m;
}