default LazyFutureStream<U> control(final Function<Supplier<U>,Supplier<U>> fn){
  final Queue queue=toQueue();
  return fromStream(queue.streamControl(getSubscription(),fn));
}

default LazyFutureStream < U > control ( final Function < Supplier < U > , Supplier < U > > fn ) { final Queue queue = toQueue ( ) ; return fromStream ( queue . streamControl ( getSubscription ( ) , fn ) ) ; }
allows clients to control the emission of data for the next phase of the stream . the user specified function can delay , drop , or change elements
