Is this a bus or a train?
This is a bus.
   src        edge_attr  dst
0    0   to the left of    3
1    0   to the left of    2
2    2   to the left of    5
3    2   to the left of    4
4    2  to the right of    0
5    3  to the right of    0
6    3   to the left of    4
7    4  to the right of    2
8    4  to the right of    3
9    5  to the right of    2