def _node_add_without_peer_container(self, node_sum, child_other):
        '''_node_add_without_peer_container

        Low-level api: Apply delta child_other to node_sum when there is no peer
        of child_other can be found under node_sum. child_other is a container
        node. Element node_sum will be modified during the process.

        Parameters
        ----------

        node_sum : `Element`
            A config node in a config tree.

        child_other : `Element`
            A child of a config node in another config tree. This child has no
            peer under node_sum.

        Returns
        -------

        None
            There is no return of this method.
        '''

        e = deepcopy(child_other)
        node_sum.append(self._del_attrib(e))