@abc.abstractmethod<EOL><INDENT>def delete_router_precommit(self, context, router_context):<DEDENT>
pass<EOL>
Perform operations specific to the routertype in
        preparation for the deletion of a router.

        :param context: the neutron context of the request
        :param router_context: RouterContext instance describing the current
                               state of the router, prior to the call to delete
                               it.

        Delete router resources previously allocated by this routertype
        driver for a router. Called inside transaction context on session.
        Runtime errors are not expected, but raising an exception will
        result in rollback of the transaction.