What is the fence made of?
The fence is made of metal.
    src        edge_attr  dst
0     0  to the right of   12
1     0               of    1
2     0  to the right of    7
3     1               on   13
4     1               on    3
5     2               of    1
6     3               of   13
7     6               of    1
8     6  to the right of   10
9     7   to the left of    0
10    7  to the right of   12
11    7               of    1
12    8  to the right of   14
13    8               of    1
14   10   to the left of   11
15   10   to the left of    6
16   11  to the right of   10
17   12   to the left of    0
18   12               of    1
19   12   to the left of    7
20   14   to the left of    8