code: func recognizeRegion(region string) {
  	awsRegionsMutex.Lock()
  	defer awsRegionsMutex.Unlock()
  
  	if awsRegions == nil {
  		awsRegions = sets.NewString()
  	}
  
  	if awsRegions.Has(region) {
  		klog.V(6).Infof("found AWS region %q again - ignoring", region)
  		return
  	}
  
  	klog.V(4).Infof("found AWS region %q", region)
  
  	awsRegions.Insert(region)
  }
docs: // recognizeRegion is called for each AWS region we know about.
  // It currently registers a credential provider for that region.
  // There are two paths to discovering a region:
  //  * we hard-code some well-known regions
  //  * if a region is discovered from instance metadata, we add that