What vehicles are in the yard?
The vehicles are buses.
    src        edge_attr  dst
0     0             near   10
1     0          next to   10
2     0  to the right of   19
3     0  to the right of    5
4     0   to the left of    1
5     0   to the left of   16
6     0  to the right of    8
7     1  to the right of    0
8     5   to the left of    0
9     6               in    9
10    6        parked on   21
11    6  to the right of   11
12    6               in   18
13    7   to the left of   16
14    7  to the right of   17
15    8   to the left of    0
16    9  to the right of   11
17   10             near   21
18   10          next to   21
19   10             near    0
20   11   to the left of    6
21   11   to the left of    9
22   11           behind   17
23   11   to the left of   18
24   13  to the right of   17
25   15   to the left of   16
26   15               on   21
27   16  to the right of    0
28   16  to the right of   15
29   16  to the right of    7
30   17      in front of   11
31   17   to the left of    7
32   17   to the left of   13
33   18  to the right of   11
34   19   to the left of    0
35   21   on the side of   21
36   21             near   10