def METHOD_NAME(window):
    """ Get size (width x height) of monitor on which window is located.
        :param window: Gtk window
        :type window: Gtk.Window
    """
    display = window.get_display()
    monitor = display.get_monitor_at_window(window.get_window())
    geometry = monitor.get_geometry()
    return (geometry.width, geometry.height)