What's on the sign?
The symbol is on the sign.
    src        edge_attr  dst
0     2               on    0
1     2  to the right of    7
2     3  to the right of    6
3     4  to the right of    7
4     4               on    0
5     5               on    0
6     5  to the right of    8
7     6   to the left of    3
8     7   to the left of    4
9     7               on    0
10    7   to the left of    2
11    8   to the left of    5
12    8               on    0