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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 connect(self, interface, event, object_path, handler):
 """ Connect to a DBus signal. If ``object_path`` is None, subscribe for all objects and invoke the callback with the object_path as its first argument. """

        if object_path:
            def callback(connection, sender_name, object_path,
                         interface_name, signal_name, parameters):
                return handler(*unpack_variant(parameters))
        else:
            def callback(connection, sender_name, object_path,
                         interface_name, signal_name, parameters):
                return handler(object_path, *unpack_variant(parameters))
        return self.connection.signal_subscribe(
            self.bus_name,
            interface,
            event,
            object_path,
            None,
            Gio.DBusSignalFlags.NONE,
            callback,
        )