presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/ShardIterator.java/ShardIterator/getNodeIdentifiers
class ShardIterator:    private Set<String> getNodeIdentifiers(List<Integer> nodeIds, UUID shardUuid)
    {
        Function<Integer, String> fetchNode = id -> fetchNode(id, shardUuid);
        return nodeIds.stream()
                .map(id -> nodeMap.computeIfAbsent(id, fetchNode))
                .collect(toSet());
    }