code: func (tg Group) MarshalYAML() (interface{}, error) {
  	g := &struct {
  		Targets []string       `yaml:"targets"`
  		Labels  model.LabelSet `yaml:"labels,omitempty"`
  	}{
  		Targets: make([]string, 0, len(tg.Targets)),
  		Labels:  tg.Labels,
  	}
  	for _, t := range tg.Targets {
  		g.Targets = append(g.Targets, string(t[model.AddressLabel]))
  	}
  	return g, nil
  }
docs: // MarshalYAML implements the yaml.Marshaler interface.