What is the sign on?
The sign is on the post.
   src        edge_attr  dst
0    0  to the right of    6
1    0  to the right of    5
2    1               on    0
3    1  to the right of    6
4    5   to the left of    0
5    5   to the left of    6
6    6   to the left of    0
7    6  to the right of    5
8    6   to the left of    1