@Override
    public <R> ReactorFetcher<R> map(Function<? super Tuple, ? extends R> mapFn) {
      ReactiveMapperTuple mapper = new ReactiveMapperTuple(query, session);
      return ReactorFetcherDelegate.fromReactive(mapper.map(mapFn));
    }
Default implementation for various rxjava mappers and their utilities
criteria/reactor/src/org/immutables/criteria/reactor/ReactorMappers.java