code: func (e *Engine) deleteVLANs() {
  	if err := e.ncc.Dial(); err != nil {
  		log.Fatalf("Failed to connect to NCC: %v", err)
  	}
  	defer e.ncc.Close()
  
  	e.vlanLock.Lock()
  	defer e.vlanLock.Unlock()
  
  	for k, v := range e.vlans {
  		if err := e.lbInterface.DeleteVLAN(v); err != nil {
  			log.Fatalf("Failed to remove VLAN interface %v: %v", v, err)
  		}
  		delete(e.vlans, k)
  	}
  }
docs: // deleteVLANs removes all the VLAN interfaces that have been created by this
  // engine.