pkg/relabel/relabel.go
func Process(labels labels.Labels, cfgs ...*Config) labels.Labels {
	for _, cfg := range cfgs {
		labels = relabel(labels, cfg)
		if labels == nil {
			return nil
		}
	}
	return labels
}
func Process(labels labels.Labels, cfgs ...*Config) labels.Labels {
	for _, cfg := range cfgs {
		labels = relabel(labels, cfg)
		if labels == nil {
			return nil
		}
	}
	return labels
}
// Process returns a relabeled copy of the given label set. The relabel configurations
// are applied in order of input.
// If a label set is dropped, nil is returned.
// May return the input labelSet modified.