Do you see any carriages or trains there?
Yes, there is a train.
    src        edge_attr  dst
0     0  to the right of    4
1     2  to the right of    9
2     2  to the right of    4
3     3  to the right of    8
4     3   to the left of   11
5     3  to the right of    6
6     4   to the left of    0
7     4   to the left of    2
8     6   to the left of    3
9     6   to the left of   11
10    6   to the left of    8
11    6   to the left of   10
12    8   to the left of    3
13    8   to the left of   10
14    8   to the left of   11
15    8  to the right of    6
16    9   to the left of    2
17   10  to the right of    8
18   10  to the right of    6
19   11  to the right of    8
20   11  to the right of    3
21   11  to the right of    6