clone graph

def cloneGraph(self, node):
        # write your code here
        map_table, set_visit, bfs_queue = dict(), set(), [node]
        #establish mapping relation from new graph node to old graph node
        set_visit.add(node)
        while len(bfs_queue) > 0:
            head = bfs_queue.pop(0)
            if head not in map_table.keys() and head is not None:
                map_table[head] = UndirectedGraphNode(head.label)
            if head is not None:
                for neibo in head.neighbors:
                    if neibo not in set_visit:
                        set_visit.add(neibo)
                        bfs_queue.append(neibo)
                
        #redirect mapping from old graph node to new graph node
        bfs_queue = []
        set_visit.clear()
        set_visit.add(node)
        bfs_queue.append(node)
        while len(bfs_queue) > 0:
            head = bfs_queue.pop(0)
            if head is not None:
                for neibo in head.neighbors:
                    map_table[head].neighbors.append(map_table[neibo])
                    if neibo not in set_visit:
                        set_visit.add(neibo)
                        bfs_queue.append(neibo)
                    
        if node in map_table:
            return map_table[node]
        return None