docs: public <R1, R4> State<S,R4> forEach2(Function<? super T, State<S,R1>> value2,
                                           BiFunction<? super T, ? super R1, ? extends R4> yieldingFunction) {
  
          return this.flatMap(in -> {
  
              State<S,R1> a = value2.apply(in);
              return a.map(in2 -> {
                  return yieldingFunction.apply(in, in2);
  
              });
  
          });
  
      }