def on_play_speed(self, *args):
        """Change the interval at which ``self.play`` is called to match my
        current ``play_speed``.

        """
        Clock.unschedule(self.play)
        Clock.schedule_interval(self.play, 1.0 / self.play_speed)
Change the interval at which ``self.play`` is called to match my
        current ``play_speed``.