Which kind of vehicle is in the train station?
The vehicles are trains.
    src        edge_attr  dst
0     0   to the left of    5
1     1  to the right of   11
2     2               in   18
3     2   to the left of   10
4     2   to the left of    9
5     2   to the left of   17
6     2   to the left of   11
7     2   to the left of   12
8     2   to the left of    6
9     2   to the left of   13
10    3   to the left of   13
11    3  to the right of   16
12    3   to the left of   17
13    4               on    1
14    4  to the right of    9
15    4               at   18
16    4  to the right of   18
17    4  to the right of   14
18    5   to the left of    6
19    5   to the left of   11
20    5  to the right of    0
21    6  to the right of    5
22    6  to the right of    2
23    8   to the left of   18
24    9   to the left of    4
25    9  to the right of    2
26    9  to the right of   10
27   10  to the right of    2
28   10               at   18
29   10   to the left of   12
30   10   to the left of    9
31   10               by   14
32   11  to the right of    5
33   11  to the right of    2
34   11  to the right of   14
35   11   to the left of    1
36   12  to the right of   14
37   12  to the right of   10
38   12  to the right of    2
39   13  to the right of    2
40   13  to the right of    3
41   13   to the left of   17
42   14   to the left of    4
43   14   to the left of   17
44   14   to the left of   11
45   14  to the right of   16
46   14   to the left of   12
47   16   to the left of   14
48   16   to the left of    3
49   17  to the right of   13
50   17  to the right of   14
51   17  to the right of    2
52   17  to the right of    3
53   18  to the right of    8
54   18   to the left of    4