code: func (p *criStatsProvider) getContainerUsageNanoCores(stats *runtimeapi.ContainerStats) *uint64 {
  	if stats == nil || stats.Attributes == nil {
  		return nil
  	}
  
  	p.mutex.RLock()
  	defer p.mutex.RUnlock()
  
  	cached, ok := p.cpuUsageCache[stats.Attributes.Id]
  	if !ok || cached.usageNanoCores == nil {
  		return nil
  	}
  	// return a copy of the usage
  	latestUsage := *cached.usageNanoCores
  	return &latestUsage
  }
docs: // getContainerUsageNanoCores gets the cached usageNanoCores.