private final ListMap<Integer, FastHit> hitsByNode(Result result) {
        ListMap<Integer, FastHit> hitsByNode = new ListMap<>();
        for (Hit hit : (Iterable<Hit>) result.hits()::unorderedDeepIterator) {
            if (hit instanceof FastHit fastHit) {
                ++numHitsToFill;
                hitsByNode.put(fastHit.getDistributionKey(), fastHit);
            }
        }
        return hitsByNode;
    }
Return a map of hits by their search node (partition) id
container-search/src/main/java/com/yahoo/search/dispatch/rpc/RpcProtobufFillInvoker.java