code: public Binder foldVoid(MethodHandle function) {
          if (type().returnType() == void.class) {
              return fold(function);
          } else {
              return fold(function.asType(function.type().changeReturnType(void.class)));
          }
      }
docs: Process the incoming arguments using the given handle, leaving the argument list
  unmodified.
  
  @param function the function that will process the incoming arguments. Its
  signature must match the current signature's arguments exactly.
  @return a new Binder