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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 sensor_id(self):
 """The id of the sensor of this data point. Returns: The id of the sensor that generated this datapoint. Will throw an AttributeError if no sensor id was found in the underlyign data. """

        if hasattr(self, '_sensor_id'):
            return self._sensor_id
        relationships = self._json_data.get('relationships')
        sensor_id = relationships.get('sensor').get('data').get('id')
        self._sensor_id = sensor_id
        return sensor_id