docs: public static <T, R1, R> Optional<R> forEach2(Optional<? extends T> value1, Function<? super T, Optional<R1>> value2,
                                                   BiFunction<? super T, ? super R1, ? extends R> yieldingFunction) {
  
          return value1.flatMap(in -> {
  
              Optional<R1> a = value2.apply(in);
              return a.map(in2 -> yieldingFunction.apply(in,  in2));
              });
  
  
  
      }