The frame widget is a Bin that surrounds its child with a
decorative frame and an optional label. If present, the label is
drawn in a gap in the top side of the frame. The position of the
label can be controlled with set_label_align().
Used to visually group objects.
GTK.Frame("Title")->add(GTK.Label("Contents"))
GTK.Frame()->add(GTK.Label("Contents"))
GTK.Frame()->add(GTK.Label("Contents"))->set_shadow_type(GTK.SHADOW_IN)