docs: MapWithProtoValuesFluentAssertion<M> usingConfig(FluentEqualityConfig newConfig) {
      Subject.Factory<MapWithMessageValuesSubject<K, M>, Map<K, M>> factory =
          mapWithProtoValues(newConfig);
      MapWithMessageValuesSubject<K, M> newSubject = check().about(factory).that(actual());
      if (internalCustomName() != null) {
        newSubject = newSubject.named(internalCustomName());
      }
      return new MapWithProtoValuesFluentAssertionImpl<>(newSubject);
    }