ty of the transaction.

        The method accepts key=value pairs. The key has to be prefixed with
        an underscore separated identifier of the client application.

        In the following example Software-Center sets an application name
        and icon:

        >>> Transaction.set_meta_data(sc_icon="shiny", sc_app="xterm")

        :param reply_handler: Callback function. If specified in combination
            with error_handler the method will be called asynchrounsouly.
        :param error_handler: Errback function. In case of an error the given
            callback gets the corresponding exception instance.
        :param defer: Run the method asynchrounsly and return a defer.Deferred.
            This options is only available as a keyword.

        :raises: aptdaemon.errors.ForeignTransaction, dbus.DBusException
        rg