def set_servo_pulsewidth(self, user_gpio, pulsewidth):
        """
        Starts (500-2500) or stops (0) servo pulses on the GPIO.
         user_gpio:= 0-31.
        pulsewidth:= 0 (off),
                     500 (most anti-clockwise) - 2500 (most clockwise).
        The selected pulsewidth will continue to be transmitted until
        changed by a subsequent call to set_servo_pulsewidth.
        The pulsewidths supported by servos varies and should probably
        be determined by experiment. A value of 1500 should always be
        safe and represents the mid-point of rotation.
        You can DAMAGE a servo if you command it to move beyond its
        limits.
        ...
        yield from pi.set_servo_pulsewidth(17, 0)    # off
        yield from pi.set_servo_pulsewidth(17, 1000) # safe anti-clockwise
        yield from pi.set_servo_pulsewidth(17, 1500) # centre
        yield from pi.set_servo_pulsewidth(17, 2000) # safe clockwise
        ...
        """
        res = yield from self._pigpio_aio_command(_PI_CMD_SERVO, user_gpio, int(pulsewidth))
        return _u2i(res)