code: def set_bar(self, bar, value):
          
          if bar < 0 or bar > 23:
              # Ignore out of bounds bars.
              return
          # Compute cathode and anode value.
          c = (bar if bar < 12 else bar - 12) // 4
          a = bar % 4
          if bar >= 12:
              a += 4
          # Set green LED based on 1st bit in value.
          self.set_led(c*16+a+8, 1 if value & GREEN > 0 else 0)
          # Set red LED based on 2nd bit in value.
          self.set_led(c*16+a, 1 if value & RED > 0 else 0)
docs: Set bar to desired color.  Bar should be a value of 0 to 23, and value
          should be OFF, GREEN, RED, or YELLOW.