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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 add_x10_device(self, housecode, unitcode, feature='OnOff'):
 """Add an X10 device based on a feature description. Current features are: - OnOff - Dimmable - Sensor - AllUnitsOff - AllLightsOn - AllLightsOff """

        device = insteonplm.devices.create_x10(self, housecode,
                                               unitcode, feature)
        if device:
            self.devices[device.address.id] = device
        return device