docs: def countdown(self, interval: float = 0.5):
          """
          Display a numeric countdown from 5
          :param interval: The interval in seconds for each number.
          """
          for c in '54321':
              self.char_on(c)
              time.sleep(interval * 0.66667)
              self.all_off()
              time.sleep(interval * 0.33333)