Is this a bus or a train?
This is a bus.
    src        edge_attr  dst
0     0  to the right of    8
1     1  to the right of    8
2     1  to the right of    6
3     2               on   14
4     3   to the left of   12
5     3       sitting on    2
6     5   to the left of   12
7     6   to the left of    1
8     7  to the right of   13
9     7   to the left of   11
10    7  to the right of   12
11    8   to the left of    1
12    8   to the left of    0
13   11  to the right of    7
14   11  to the right of   13
15   12  to the right of    3
16   12  to the right of    5
17   12   to the left of    7
18   12   to the left of   13
19   13   to the left of   11
20   13  to the right of   12
21   13   to the left of    7