code: func (c *totalVolumesCollector) Collect(ch chan<- prometheus.Metric) {
  	for stateName, pluginCount := range c.getVolumeCount() {
  		for pluginName, count := range pluginCount {
  			metric, err := prometheus.NewConstMetric(totalVolumesDesc,
  				prometheus.GaugeValue,
  				float64(count),
  				pluginName,
  				stateName)
  			if err != nil {
  				klog.Warningf("Failed to create metric : %v", err)
  			}
  			ch <- metric
  		}
  	}
  }
docs: // Collect implements the prometheus.Collector interface.