code: func (t *awsTagging) initFromTags(tags []*ec2.Tag) error {
  	legacyClusterID, newClusterID, err := findClusterIDs(tags)
  	if err != nil {
  		return err
  	}
  
  	if legacyClusterID == "" && newClusterID == "" {
  		glog.Errorf("Tag %q nor %q not found; Kubernetes may behave unexpectedly.", TagNameKubernetesClusterLegacy, TagNameKubernetesClusterPrefix+"...")
  	}
  
  	return t.init(legacyClusterID, newClusterID)
  }
docs: // Extracts a clusterID from the given tags, if one is present
  // If no clusterID is found, returns "", nil
  // If multiple (different) clusterIDs are found, returns an error