Call `show()` on each top widget or `show_all()` if only one is known.
        Otherwise does nothing.

def show(self):
        """
        Call `show()` on each top widget or `show_all()` if only one is known.
        Otherwise does nothing.
        """
        top = self.get_top_widget()
        if isinstance(top, (list, tuple)):
            for t in top:
                if t is not None:
                    t.show()
        elif top is not None:
            top.show_all()