code: func (t *Target) URL() *url.URL {
  	params := url.Values{}
  
  	for k, v := range t.params {
  		params[k] = make([]string, len(v))
  		copy(params[k], v)
  	}
  	for _, l := range t.labels {
  		if !strings.HasPrefix(l.Name, model.ParamLabelPrefix) {
  			continue
  		}
  		ks := l.Name[len(model.ParamLabelPrefix):]
  
  		if len(params[ks]) > 0 {
  			params[ks][0] = l.Value
  		} else {
  			params[ks] = []string{l.Value}
  		}
  	}
  
  	return &url.URL{
  		Scheme:   t.labels.Get(model.SchemeLabel),
  		Host:     t.labels.Get(model.AddressLabel),
  		Path:     t.labels.Get(model.MetricsPathLabel),
  		RawQuery: params.Encode(),
  	}
  }
docs: // URL returns a copy of the target's URL.