what is the correct way to delete the Custom Widgets

[yadmtr]

Please tell me what is the correct way to delete the Custom Widgets?

mutable struct ComposedWidget <: Gtk.GtkBox
    handle::Ptr{Gtk.GObject}
    btn # handle to child
    tv # handle to child

    function ComposedWidget(label)
        vbox = GtkBox(:v)
        btn = GtkButton(label)
        tv = GtkTextView()
        push!(vbox,btn,tv)
        set_gtk_property!(vbox,:expand,tv,true)
        set_gtk_property!(vbox,:spacing,10)
        w = new(vbox.handle, btn, tv)
        return Gtk.gobject_move_ref(w, vbox)
    end
end

c = ComposedWidget("My Button")
win = GtkWindow("Composed Widget",400,200)
push!(win, c)
showall(win)