What is the fence on?
The fence is on the bridge.
    src        edge_attr  dst
0     1   to the left of    8
1     1   to the left of    4
2     1  to the right of    2
3     2   to the left of    8
4     2   to the left of    4
5     2   to the left of    1
6     4  to the right of    2
7     4  to the right of    1
8     4  to the right of    9
9     8  to the right of    1
10    8  to the right of    9
11    8               on    5
12    8  to the right of    2
13    9   to the left of    4
14    9          wearing    1
15    9   to the left of    8
16    9      standing by    7
17    9          wearing    6