What vehicle is in front of the healthy tree?
The vehicle is a train.
    src        edge_attr  dst
0     0  to the right of    1
1     0  to the right of    4
2     1   to the left of    5
3     1   to the left of    0
4     3             near    5
5     3               by    5
6     4               by    5
7     4             near    5
8     4   to the left of    0
9     4           behind    5
10    4   to the left of    5
11    5             near    4
12    5  to the right of    4
13    5  to the right of    1
14    5      in front of    4
15    5             near    3