code: func NewLabelCopier(separator string, storedLabels, ignoredLabels []string) (*LabelCopier, error) {
  	return &LabelCopier{
  		labelSeparator: separator,
  		storedLabels:   makeStoredLabels(storedLabels),
  		ignoredLabels:  makeIgnoredLabels(ignoredLabels),
  	}, nil
  }
docs: // NewLabelCopier creates a new instance of LabelCopier type