private FlowableTransformer<AccumulatedResult, AccumulatedResult> transformer() {
    return FlowableTransformers.expand(r -> r.isLast() ?
            maybeClearScroll(r.result).toFlowable() :
            ops.nextScroll(r.result.scrollId().get()).toFlowable().map(r::next));
  }
Duration to keep scroll context alive.
criteria/elasticsearch/src/org/immutables/criteria/elasticsearch/Scrolling.java