Blink all the lights on and off at once.
        NOTE! Does not remember prior state of lights and will finish
        with all lights off.
        :param interval: The length in seconds of an ON/OFF cycle
        :param n: How many times to cycle ON and OFF
        :return:

def blink(self, interval: float = 0.2, n: int = 3):
        """
        Blink all the lights on and off at once.
        NOTE! Does not remember prior state of lights and will finish
        with all lights off.
        :param interval: The length in seconds of an ON/OFF cycle
        :param n: How many times to cycle ON and OFF
        :return:
        """
        for i in range(n):
            self.all_on()
            time.sleep(interval / 2)
            self.all_off()
            time.sleep(interval / 2)