Do you see a bus or a train that are yellow?
Yes, the train is yellow.
    src        edge_attr  dst
0     0   to the left of    4
1     1   to the left of    3
2     2               on    7
3     3  to the right of    1
4     3  to the right of    4
5     3  to the right of   14
6     3  to the right of    8
7     4   to the left of    3
8     4   to the left of   14
9     4  to the right of    0
10    7   to the left of    9
11    8   to the left of   12
12    8   to the left of    3
13    8   to the left of   14
14    9  to the right of   16
15    9  to the right of    7
16   12  to the right of    8
17   14  to the right of    8
18   14  to the right of    4
19   14   to the left of    3
20   16   to the left of    9