public U call(DeferredCloser closer, Peeker peeker) throws Exception {
              return function.apply(
                  closer,
                  peeker.getDone(future1),
                  peeker.getDone(future2),
                  peeker.getDone(future3),
                  peeker.getDone(future4),
                  peeker.getDone(future5));
            }

            @Override

      hasPeeked = false;
      peekedElement = null;
      return result;
    }

    @Override
    public void remove() {
      checkState(!hasPeeked, "Can't remove after you've peeked at next");
      iterator.remove();
    }

    @Override
    @ParametricNullness
    public E peek() {
      if (!hasPeeked) {
        peekedElement = iterator.next();