ClosingFuture<V5> future5) {
      super(true, ImmutableList.of(future1, future2, future3, future4, future5));
      this.future1 = future1;
      this.future2 = future2;
      this.future3 = future3;
      this.future4 = future4;
      this.future5 = future5;
    }

    /**
     * Returns a new {@code ClosingFuture} pipeline step derived from the inputs by applying a