presto-main/src/main/java/io/prestosql/execution/scheduler/SqlQueryScheduler.java/SqlQueryScheduler/getStageInfo
class SqlQueryScheduler:    public StageInfo getStageInfo()
    {
        Map<StageId, StageInfo> stageInfos = stages.values().stream()
                .map(SqlStageExecution::getStageInfo)
                .collect(toImmutableMap(StageInfo::getStageId, identity()));

        return buildStageInfo(rootStageId, stageInfos);
    }