@Override
            public DataList<D> get() throws InterruptedException, ExecutionException {
            DataList<D> result = null;
            for (CompletableFuture<DataList<D>> future : futures) {
                if (result == null)
                    result = future.get();
                else
                    future.get();
            }
            complete(result);
            return result;
        }
A future which on get calls get on all its given futures and sets the value returned from the
first given future as its result.
container-core/src/main/java/com/yahoo/processing/Response.java