What is the vehicle that is on the path the cow is in front of?
The vehicle is a truck.
    src        edge_attr  dst
0     0   to the left of    1
1     1  to the right of    0
2     2       grazing on    3
3     2      in front of   11
4     2  to the right of    3
5     3   to the left of    2
6     6      in front of    9
7     6      in front of    7
8     6      in front of   10
9     6               on   11
10    6   to the left of    8
11    6  to the right of   11
12    7           behind    8
13    7           behind    6
14    8               on   11
15    8      in front of    9
16    8      in front of    7
17    8  to the right of    6
18    8      in front of   10
19   10           behind    8
20   11   to the left of    6