pyGtk3 Do dialogues have to have a parent? If so, how do you call them from a script?

I can have a script that calls a window, but when I try to raise a dialogue with parent = None, I get:

Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.

What parent can I map this this to? It seems I can map it to a dummy parent, but will this cause things to break and people to die?

Code from http://python-gtk-3-tutorial.readthedocs.io/en/latest/dialogs.html#messagedialog where it is called from a parent window... but I want to be able to pop this up as I'm running through a terminal script.

Edit: Some poking around (and also provide by an answer below) yielded that using Gtk.Window() as the first argument below (instead of none) does get rid of the message...

def on_question():
    dialog = Gtk.MessageDialog(None, 0, Gtk.MessageType.QUESTION,
        Gtk.ButtonsType.YES_NO, "This is an QUESTION MessageDialog")
    dialog.format_secondary_text(
        "And this is the secondary text that explains things.")
    response = dialog.run()
    if response == Gtk.ResponseType.YES:
        print("QUESTION dialog closed by clicking YES button")
    elif response == Gtk.ResponseType.NO:
        print("QUESTION dialog closed by clicking NO button")

    dialog.destroy()

Solution

I will made the above comment an answer. You may have a w = Gtk.Window() somewhere in your code (it may be inside function body) and pass that w to on_question:

def on_question(parent=None):
    dialog = Gtk.MessageDialog(parent, 0, Gtk.MessageType.QUESTION,
        Gtk.ButtonsType.YES_NO, "This is an QUESTION MessageDialog")
....
w = Gtk.Window()
on_question(w)

def on_question():
    dialog = Gtk.MessageDialog(Gtk.Window(), 0, Gtk.MessageType.QUESTION,
        Gtk.ButtonsType.YES_NO, "This is an QUESTION MessageDialog")

The Gtk-message it's gone, if that is the only problem.