code: def _set_speed(self, motor, speed):
          
          self._validate_motor(motor)
          en, in1, in2 = self._motors[motor-1]
  
          if speed == 0:
              en.pwm_stop()
              in1.set(False)
              in2.set(False)
          elif speed > 0:
              en.pwm_start(abs(speed))
              in1.set(True)
              in2.set(False)
          else:
              en.pwm_start(abs(speed))
              in1.set(False)
              in2.set(True)
docs: Change the speed of a motor on the controller.
  
          :param motor: The motor to change.
          :type motor: ``int``
  
          :param speed: Speed from -100 to +100, 0 is stop
          :type speed: ``int``