code: func BandwidthReporter(rep metrics.Reporter) Option {
  	return func(cfg *Config) error {
  		if cfg.Reporter != nil {
  			return fmt.Errorf("cannot specify multiple bandwidth reporter options")
  		}
  
  		cfg.Reporter = rep
  		return nil
  	}
  }
docs: // BandwidthReporter configures libp2p to use the given bandwidth reporter.