presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/BucketShards.java/BucketShards/BucketShards
class BucketShards:    public BucketShards(OptionalInt bucketNumber, Set<ShardNodes> shards)
    {
        this.bucketNumber = requireNonNull(bucketNumber, "bucketNumber is null");
        this.shards = ImmutableSet.copyOf(requireNonNull(shards, "shards is null"));
    }