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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def polarity(self):
 """ Sets the polarity of the motor. With `normal` polarity, a positive duty cycle will cause the motor to rotate clockwise. With `inversed` polarity, a positive duty cycle will cause the motor to rotate counter-clockwise. Valid values are `normal` and `inversed`. """

        self._polarity, value = self.get_attr_string(self._polarity, 'polarity')
        return value