presto-main/src/main/java/io/prestosql/execution/scheduler/FixedBucketNodeMap.java/FixedBucketNodeMap/FixedBucketNodeMap
class FixedBucketNodeMap:    public FixedBucketNodeMap(ToIntFunction<Split> splitToBucket, List<InternalNode> bucketToNode)
    {
        super(splitToBucket);
        this.bucketToNode = ImmutableList.copyOf(requireNonNull(bucketToNode, "bucketToNode is null"));
    }