code: func (m MetricsWithReset) Install(c *mux.PathRecorderMux) {
  	register()
  	defaultMetricsHandler := prometheus.Handler().ServeHTTP
  	c.HandleFunc("/metrics", func(w http.ResponseWriter, req *http.Request) {
  		if req.Method == "DELETE" {
  			apimetrics.Reset()
  			etcdmetrics.Reset()
  			io.WriteString(w, "metrics reset\n")
  			return
  		}
  		defaultMetricsHandler(w, req)
  	})
  }
docs: // Install adds the MetricsWithReset handler