[Vala] Stop Gtk.Spinner?

["webierta gmail com" <webierta gmail com>]

how can I stop this widget in Genie when I press a key?

// compila con valac --pkg gtk+-3.0 nombre_archivo.gs
uses Gtk
init    
    Gtk.init (ref args) 
    var test = new TestVentana ()   
    test.show_all ()    
    Gtk.main ()

class TestVentana: Window

    spinner: Gtk.Spinner    

    init        
        title = "Ejemplo Gtk"       
        default_height = 300
        default_width = 300
        border_width = 50       
        window_position = WindowPosition.CENTER     
        destroy.connect(Gtk.main_quit)

        var spinner = new Gtk.Spinner ()        
        spinner.active = true       
        add (spinner)

        //key_press_event += tecla // OBSOLETO
        key_press_event.connect(tecla)  

    def tecla(key : Gdk.EventKey):bool      
        //spinner.active = false   ???
        //spinner.stop ()          ???
        return true