code: func (a *Aliases) Add(alias, mac, iface string) error {
  	a.mtx.Lock()
  	defer a.mtx.Unlock()
  
  	// Create a buffer to store the encoded MAC, interface pair.
  	buf, err := EncodeFromMacIface(mac, iface)
  	if err != nil {
  		return err
  	}
  
  	// We don't have to worry about the key existing, as we will update it
  	// provided it exists.
  	return a.db.Update(func(tx *bolt.Tx) error {
  		bucket := tx.Bucket([]byte(bucketName))
  		return bucket.Put([]byte(alias), buf.Bytes())
  	})
  }
docs: // Add updates an alias entry or adds a new alias entry. If the alias already
  // exists it is just overwritten.