@IgnoreJRERequirement // Users will use this only if they're already using streams.
  public static <E> Collector<E, ?, ImmutableSortedMultiset<E>> toImmutableSortedMultiset(
      Comparator<? super E> comparator) {
    return toImmutableSortedMultiset(comparator, Function.identity(), e -> 1);
  }

  /**
   * Returns a {@code Collector} that accumulates elements into an {@code ImmutableSortedMultiset}

                && ms1.entrySet().asList().equals(ms2.entrySet().asList())
                && ms1.comparator().equals(ms2.comparator());
    CollectorTester.of(
            ImmutableSortedMultiset.<String>toImmutableSortedMultiset(
                String.CASE_INSENSITIVE_ORDER),
            equivalence)
        .expectCollects(ImmutableSortedMultiset.emptyMultiset(String.CASE_INSENSITIVE_ORDER))
        .expectCollects(