code: func (e *RuntimeStatsColl) GetRootStats(planID string) *RuntimeStats {
  	e.mu.Lock()
  	defer e.mu.Unlock()
  	runtimeStats, exists := e.rootStats[planID]
  	if !exists {
  		runtimeStats = &RuntimeStats{}
  		e.rootStats[planID] = runtimeStats
  	}
  	return runtimeStats
  }
docs: // GetRootStats gets execStat for a executor.