presto-main/src/main/java/io/prestosql/event/QueryMonitor.java/QueryMonitor/getCpuDistributions
class QueryMonitor:    private static List<StageCpuDistribution> getCpuDistributions(QueryInfo queryInfo)
    {
        if (!queryInfo.getOutputStage().isPresent()) {
            return ImmutableList.of();
        }

        ImmutableList.Builder<StageCpuDistribution> builder = ImmutableList.builder();
        populateDistribution(queryInfo.getOutputStage().get(), builder);

        return builder.build();
    }