code: func (c *bcacheCollector) Update(ch chan<- prometheus.Metric) error {
  	stats, err := c.fs.BcacheStats()
  	if err != nil {
  		return fmt.Errorf("failed to retrieve bcache stats: %v", err)
  	}
  
  	for _, s := range stats {
  		c.updateBcacheStats(ch, s)
  	}
  	return nil
  }
docs: // Update reads and exposes bcache stats.
  // It implements the Collector interface.