docs: public static <V, C extends Set<? extends V>> ImmutableListMultimap<V, C> makeSetElementsToContainersMultimap(
        final Iterable<C> sets) {
      // because these are sets we can safely use a list multimap without having to worry
      // about duplicates
      final ImmutableListMultimap.Builder<V, C> ret = ImmutableListMultimap.builder();
  
      for (final C set : sets) {
        for (final V item : set) {
          ret.put(item, set);
        }
      }
  
      return ret.build();
    }