Which color is the train the railroad contains?
The train is yellow.
    src        edge_attr  dst
0     0  to the right of    8
1     0  to the right of    4
2     0  to the right of    7
3     0   to the left of    5
4     1      in front of    8
5     1          contain    0
6     1  to the right of    7
7     3  to the right of    7
8     3   to the left of    5
9     4   to the left of    0
10    5  to the right of    0
11    5  to the right of    3
12    6               on    1
13    7      in front of    8
14    7   to the left of    3
15    7   to the left of    1
16    7   to the left of    0
17    8           behind    7
18    8           behind    1
19    8               by    7
20    8   to the left of    0