Update current configuration.

        This method is usually called after loading a `Cluster`
        instance from a persistent storage. Note that not all fields
        are actually updated, but only those that can be safely
        updated.

def update_config(self, cluster_config, login_config):
        """Update current configuration.

        This method is usually called after loading a `Cluster`
        instance from a persistent storage. Note that not all fields
        are actually updated, but only those that can be safely
        updated.
        """

        oldvalue = self.__update_option(cluster_config, 'ssh_to', 'ssh_to')
        if oldvalue:
            log.debug("Attribute 'ssh_to' updated: %s -> %s", oldvalue, self.ssh_to)