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
}
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
}
// MarshalYAML implements the yaml.Marshaler interface.