What is the fence made of?
The fence is made of metal.
    src        edge_attr  dst
0     0  to the right of   15
1     0   to the left of    6
2     0   to the left of   20
3     1  to the right of    2
4     2   to the left of    1
5     3        on top of    4
6     4            above    5
7     5  to the right of   19
8     5            under    4
9     5             near   19
10    6  to the right of    7
11    6  to the right of    0
12    7   to the left of    6
13    7  to the right of   13
14    8        on top of   21
15   13   to the left of    7
16   13   to the left of   20
17   14  to the right of   19
18   15   to the left of   16
19   15   to the left of    0
20   15               by    0
21   16   to the left of   20
22   16  to the right of   15
23   16        on top of   21
24   18        on top of   17
25   19   to the left of   14
26   19   to the left of    5
27   19          next to    5
28   20        on top of   21
29   20  to the right of   13
30   20  to the right of    0
31   20  to the right of   16