Set the PWM frequency.

        :Parameters:
          pwm : `int`
            The PWN frequency to set in hertz.
          device : `int`
            The device is the integer number of the hardware devices ID and
            is only used with the Pololu Protocol.
          message : `bool`
            If set to `True` a text message will be returned, if set to `False`
            the integer stored in the Qik will be returned.

        :Returns:
          A text message or an int. See the `message` parameter above.

def _setPWMFrequency(self, pwm, device, message):
        """
        Set the PWM frequency.

        :Parameters:
          pwm : `int`
            The PWN frequency to set in hertz.
          device : `int`
            The device is the integer number of the hardware devices ID and
            is only used with the Pololu Protocol.
          message : `bool`
            If set to `True` a text message will be returned, if set to `False`
            the integer stored in the Qik will be returned.

        :Returns:
          A text message or an int. See the `message` parameter above.
        """
        value = self._CONFIG_PWM_TO_VALUE.get(pwm)

        if value is None:
            msg = "Invalid frequency: {}".format(pwm)
            self._log and self._log.error(msg)
            raise ValueError(msg)

        self._deviceConfig[device]['pwm'] = value
        return self._setConfig(self.PWM_PARAM, value, device, message)