presto-elasticsearch/src/main/java/io/prestosql/elasticsearch/client/NodesResponse.java/NodesResponse/NodesResponse
class NodesResponse:    @JsonCreator
    public NodesResponse(@JsonProperty("nodes") Map<String, Node> nodes)
    {
        requireNonNull(nodes, "nodes is null");

        this.nodes = ImmutableMap.copyOf(nodes);
    }