code: func PrivateNetwork(prot pnet.Protector) Option {
  	return func(cfg *Config) error {
  		if cfg.Protector != nil {
  			return fmt.Errorf("cannot specify multiple private network options")
  		}
  
  		cfg.Protector = prot
  		return nil
  	}
  }
docs: // PrivateNetwork configures libp2p to use the given private network protector.