Set expression for the math service.
            
            @param sensor_id (int) - Sensor id of the sensor the service is connected to.
            @param service_id (int) - Service id of the service for which to set the expression.
            @param method (string) - The get method name.
                    
            @return (bool) - Boolean indicating whether ServicesSetExpression was successful.

def ServicesGetMetod (self, sensor_id, service_id, method):
        """
            Set expression for the math service.
            
            @param sensor_id (int) - Sensor id of the sensor the service is connected to.
            @param service_id (int) - Service id of the service for which to set the expression.
            @param method (string) - The get method name.
                    
            @return (bool) - Boolean indicating whether ServicesSetExpression was successful.
        """
        if self.__SenseApiCall__('/sensors/{0}/services/{1}/{2}.json'.format(sensor_id, service_id, method), 'GET'):
            return True
        else:
            self.__error__ = "api call unsuccessful"
            return False