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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 AddAC(self, device_name, model_name):
    '''Convenience method to add an AC object

    You have to specify a device name which must be a valid part of an object
    path, e. g. "mock_ac", and an arbitrary model name.

    Please note that this does not set any global properties such as
    "on-battery".

    Returns the new object path.
    '''
    path = '/org/freedesktop/UPower/devices/' + device_name
    self.AddObject(path,
                   DEVICE_IFACE,
                   {
                       'PowerSupply': dbus.Boolean(True, variant_level=1),
                       'Model': dbus.String(model_name, variant_level=1),
                       'Online': dbus.Boolean(True, variant_level=1),
                   },
                   [])
    self.EmitSignal(MAIN_IFACE, 'DeviceAdded', self.device_sig_type, [path])
    return path