What is the flag on?
The flag is on the post.
    src        edge_attr  dst
0     0               on    4
1     0   to the left of   13
2     0   to the left of   12
3     0   to the left of   14
4     0   to the left of    8
..  ...              ...  ...
66   14   to the left of   12
67   14   to the left of    8
68   14   to the left of    9
69   15   to the left of   10
70   15  to the right of    5

[71 rows x 3 columns]