What vehicle is in front of the fence?
The vehicle is a train.
    src        edge_attr  dst
0     1   to the left of   10
1     2  to the right of   11
2     2  to the right of   10
3     5  to the right of   15
4     6   to the left of    9
5     7  to the right of   11
6     8               of   11
7     8  to the right of   11
8     9  to the right of    6
9    10  to the right of    1
10   10   to the left of    2
11   11   to the left of    7
12   11   to the left of    8
13   11   to the left of    2
14   11      in front of   14
15   12  to the right of   15
16   13               on    0
17   14           behind   11
18   14           beside   13
19   15               of   11
20   15   to the left of    5
21   15   to the left of   12