Are there either yellow trains or buses?
Yes, there is a yellow train.
    src        edge_attr  dst
0     1   to the left of   12
1     1   to the left of    3
2     1  to the right of   11
3     1   to the left of    6
4     3   to the left of    6
5     3  to the right of    1
6     4  to the right of   11
7     4  to the right of    8
8     4  to the right of   10
9     6  to the right of    1
10    6  to the right of    3
11    8               in   11
12    8   to the left of    4
13   10   to the left of    4
14   11   to the left of    1
15   11   to the left of    4
16   12  to the right of    1
17   12               of    4