mapEntry("c", 4));
  }

  public void testFlatteningToImmutableListMultimap() {
    Collector<String, ?, ImmutableListMultimap<Character, Character>> collector =
        ImmutableListMultimap.flatteningToImmutableListMultimap(
            str -> str.charAt(0), str -> Chars.asList(str.substring(1).toCharArray()).stream());
    BiPredicate<Multimap<?, ?>, Multimap<?, ?>> equivalence =
        Equivalence.equals()