The format of node is similar to add_node.
        If node contains a key 'cluster_node'
        whose value is an instance of ClusterNode,
        it will be used directly.

def add_nodes(self, nodes):
        '''The format of node is similar to add_node.
        If node contains a key 'cluster_node'
        whose value is an instance of ClusterNode,
        it will be used directly.
        '''
        new_nodes, master_map = self._add_nodes_as_master(nodes)

        for n in new_nodes:
            if n.name not in master_map:
                continue
            master_name = master_map[n.name]
            target = self.get_node(master_name)
            if not target:
                raise NodeNotFound(master_name)
            n.replicate(target.name)
            n.flush_cache()
            target.flush_cache()