Which kind of vehicle is silver?
The vehicle is a train.
    src        edge_attr  dst
0     2  to the right of   14
1     3  to the right of   14
2     5   to the left of   12
3     6   to the left of   12
4     7  to the right of   14
5     7  to the right of   10
6     9   to the left of   12
7    10   to the left of    7
8    10   to the left of   12
9    11  to the right of   13
10   12  to the right of    6
11   12  to the right of   10
12   12  to the right of    9
13   12  to the right of    5
14   13   to the left of   11
15   14   to the left of    3
16   14   to the left of    2
17   14   to the left of    7