presto-main/src/main/java/io/prestosql/execution/scheduler/FixedCountScheduler.java/FixedCountScheduler/FixedCountScheduler
class FixedCountScheduler:    public FixedCountScheduler(SqlStageExecution stage, List<InternalNode> partitionToNode)
    {
        requireNonNull(stage, "stage is null");
        this.taskScheduler = stage::scheduleTask;
        this.partitionToNode = requireNonNull(partitionToNode, "partitionToNode is null");
    }