What's pulled by the locomotive?
The cars are pulled by the train engine.
    src        edge_attr  dst
0     0   to the left of    2
1     0   to the left of   11
2     0   to the left of    6
3     0               of   10
4     0  to the right of    5
..  ...              ...  ...
63   13  to the right of    1
64   14  to the right of   10
65   14  to the right of    4
66   14  to the right of   13
67   14  to the right of   12

[68 rows x 3 columns]