Updates a router

def update_router(self, router, name=None, admin_state_up=None, **kwargs):
        '''
        Updates a router
        '''
        router_id = self._find_router_id(router)
        body = {}

        if 'ext_network' in kwargs:
            if kwargs.get('ext_network') is None:
                body['external_gateway_info'] = None
            else:
                net_id = self._find_network_id(kwargs.get('ext_network'))
                body['external_gateway_info'] = {'network_id': net_id}
        if name is not None:
            body['name'] = name
        if admin_state_up is not None:
            body['admin_state_up'] = admin_state_up
        return self.network_conn.update_router(
            router=router_id, body={'router': body})