code: @Override
    public void consume(SerializableConsumer<R> consumer) {
      checkNotNull(consumer, "consumer cannot be null");
  
      ConsumerStreamlet<R> consumerStreamlet = new ConsumerStreamlet<>(this, consumer);
      addChild(consumerStreamlet);
    }
docs: Applies the consumer function for every element of this streamlet
  @param consumer The user supplied consumer function that is invoked for each element