$ python3 my_bfs.py 
頂点3から頂点7への経路: 3 2 1 0 7 
0, adj = {1, 7}, 2, 3, 1
1, adj = {0, 2, 6}, 2, 2, 2
2, adj = {1, 3, 5}, 2, 1, 3
3, adj = {2, 4, 5}, 2, 0, None
4, adj = {3, 5}, 2, 1, 3
5, adj = {2, 3, 4, 6}, 2, 1, 3
6, adj = {1, 5}, 2, 2, 5
7, adj = {0}, 2, 4, 0