Is there either a fence or a train?
Yes, there is a train.
    src        edge_attr  dst
0     0   to the left of    6
1     1   to the left of    8
2     2  to the right of    6
3     2  to the right of    9
4     4  to the right of    8
5     6   to the left of    2
6     6  to the right of    0
7     7  to the right of    9
8     8  to the right of    1
9     8   to the left of    4
10    9   to the left of    2
11    9   to the left of    7