What is the vehicle to the left of the trailer called?
The vehicle is a truck.
    src        edge_attr  dst
0     0          pulling    1
1     0  to the right of    2
2     0   to the left of    1
3     0  to the right of   15
4     0  to the right of    8
..  ...              ...  ...
79   19               of    0
80   19   to the left of    1
81   19  to the right of    5
82   19  to the right of    9
83   19  to the right of    8

[84 rows x 3 columns]