What vehicle is in front of the tree?
The vehicle is a bus.
    src        edge_attr  dst
0     0   to the left of   10
1     1      in front of    9
2     1  to the right of    3
3     1  to the right of    8
4     1  to the right of    5
5     1  to the right of    2
6     1   to the left of   10
7     2   to the left of    1
8     3   to the left of    9
9     3   to the left of    1
10    3           behind    5
11    4  to the right of    8
12    5      in front of    3
13    5   to the left of    1
14    7   to the left of    9
15    8   to the left of    1
16    8   to the left of    4
17    9               on   10
18    9           behind    1
19    9  to the right of    3
20    9  to the right of    7
21   10  to the right of    0
22   10  to the right of    1