code: public static <K, M extends Message>
        SetMultimapWithProtoValuesSubject<?, K, M, SetMultimap<K, M>> assertThat(
            @NullableDecl SetMultimap<K, M> setMultimap) {
      return assertAbout(protos()).that(setMultimap);
    }
docs: Assert on a {@link Multimap} with {@link Message} values.
  
  <p>This allows for the equality configurations on {@link ProtoSubject} to be applied to all
  comparison tests available on {@link MultimapSubject.UsingCorrespondence}.