code: func (this *LabelCopier) Copy(in map[string]string, out map[string]string) {
  	labels := make([]string, 0, len(in))
  
  	for key, value := range in {
  		if mappedKey, exists := this.storedLabels[key]; exists {
  			out[mappedKey] = value
  		}
  
  		if _, exists := this.ignoredLabels[key]; !exists {
  			labels = append(labels, fmt.Sprintf("%s:%s", key, value))
  		}
  	}
  
  	sort.Strings(labels)
  	out[core.LabelLabels.Key] = strings.Join(labels, this.labelSeparator)
  }
docs: // Copy copies the given set of pod labels into a set of metric labels, using the following logic:
  // - all labels, unless found in ignoredLabels, are concatenated into a Separator-separated key:value pairs and stored under core.LabelLabels.Key
  // - labels found in storedLabels are additionally stored under key provided