code: func Register(pvLister PVLister, pvcLister PVCLister) {
  	registerMetrics.Do(func() {
  		prometheus.MustRegister(newPVAndPVCCountCollector(pvLister, pvcLister))
  		prometheus.MustRegister(volumeOperationMetric)
  		prometheus.MustRegister(volumeOperationErrorsMetric)
  	})
  }
docs: // Register all metrics for pv controller.