What type of vehicle is empty, the car or the trailer?
The trailer is empty.
    src        edge_attr  dst
0     0   to the left of    3
1     0  to the right of   15
2     0  to the right of   18
3     1   to the left of   13
4     1  to the right of   11
..  ...              ...  ...
71   20  to the right of   12
72   20  to the right of    4
73   20   to the left of    1
74   21               in   22
75   23  to the right of    7

[76 rows x 3 columns]