What is on the sign?
The letter is on the sign.
     src        edge_attr  dst
0      0               on    6
1      0  to the right of    7
2      0  to the right of    9
3      0   to the left of   13
4      0   to the left of   16
..   ...              ...  ...
120   16  to the right of    1
121   16  to the right of    8
122   16  to the right of    0
123   16  to the right of    6
124   16  to the right of   14

[125 rows x 3 columns]