What vehicle is to the left of the cars?
The vehicle is a train.
    src        edge_attr  dst
0     0  to the right of    7
1     0  to the right of    2
2     0   to the left of   16
3     0  to the right of    8
4     1   to the left of    2
..  ...              ...  ...
63   20  to the right of   17
64   21   to the left of   20
65   21  to the right of   17
66   21  to the right of    5
67   21   to the left of   18

[68 rows x 3 columns]