code: def setLedN(self, led_number=0):
          
          if ( self.dev == None ): return ''
          buf = [REPORT_ID, ord('l'), led_number, 0,0,0,0,0,0]
          self.write(buf)
docs: Set the 'current LED' value for writePatternLine
          :param led_number: LED to adjust, 0=all, 1=LEDA, 2=LEDB