@Override
    public <R> RxJavaFetcher<R> map(Function<? super Tuple, ? extends R> mapFn) {
      ReactiveMapper5<T1, T2, T3, T4, T5> delegate = new ReactiveMapper5<>(query, session);
      return RxJavaFetcherDelegate.fromReactive(delegate.map(mapFn));
    }
Default implementation for various rxjava mappers and their utilities
criteria/rxjava2/src/org/immutables/criteria/repository/rxjava2/RxJavaMappers.java