Is this a truck or a train?
This is a train.
    src        edge_attr  dst
0     0  to the right of    9
1     2  to the right of    4
2     3  to the right of    6
3     4   to the left of    2
4     4   to the left of    8
5     6   to the left of    3
6     7  to the right of    9
7     8  to the right of    4
8     9   to the left of    7
9     9   to the left of   11
10    9   to the left of    0
11   11  to the right of    9