What is the van behind of, a truck or a bus?
The van is behind a truck.
     src        edge_attr  dst
0      0   to the left of   15
1      0   to the left of   11
2      0   to the left of   20
3      0  to the right of    6
4      0  to the right of   16
..   ...              ...  ...
125   23   to the left of   12
126   23           behind   18
127   23   to the left of    4
128   23  to the right of    5
129   23   to the left of   22

[130 rows x 3 columns]