if err != nil {
			return nil, nil, err
		}

		legacyregistry.RawMustRegister(metrics.NewGaugeFunc(
			&metrics.GaugeOpts{
				Subsystem: kubeletmetrics.KubeletSubsystem,
				Name:      "certificate_manager_client_ttl_seconds",
				Help: "Gauge of the TTL (time-to-live) of the Kubelet's client certificate. " +
					"The value is in seconds until certificate expiry (negative if already expired). " +