Is this a bus or a train?
This is a bus.
   src        edge_attr  dst
0    2  to the right of    3
1    3   to the left of    6
2    3   to the left of    2
3    4  to the right of    9
4    6  to the right of    9
5    6  to the right of    3
6    9   to the left of    6
7    9   to the left of    4