What material makes up that fence?
The fence is made of metal.
    src        edge_attr  dst
0     0   to the left of    2
1     0  to the right of    1
2     0  to the right of    9
3     0   to the left of   22
4     0  to the right of    7
5     1   to the left of    2
6     1   to the left of    0
7     1  to the right of    9
8     1  to the right of    7
9     1   to the left of   22
10    2   to the left of   22
11    2  to the right of    1
12    2  to the right of    0
13    2   to the left of   20
14    2   to the left of   19
15    2               of   21
16    4  to the right of    8
17    4   to the left of   18
18    5  to the right of   21
19    7   to the left of    1
20    7   to the left of    0
21    8   to the left of   18
22    8   to the left of    4
23    8   to the left of   19
24    8  to the right of   21
25    9   to the left of   21
26    9   to the left of    0
27    9   to the left of    1
28   10  to the right of   16
29   11   to the left of   21
30   12  to the right of   21
31   16   to the left of   10
32   18  to the right of    4
33   18  to the right of    8
34   19  to the right of    2
35   19  to the right of   21
36   19  to the right of    8
37   20  to the right of    2
38   20  to the right of   21
39   20  to the right of   22
40   21   to the left of   22
41   21   to the left of   20
42   21   to the left of   19
43   21  to the right of   11
44   21   to the left of   12
45   21  to the right of    9
46   21   to the left of    5
47   21   to the left of    8
48   22   to the left of   20
49   22  to the right of   21
50   22  to the right of    2
51   22  to the right of    0
52   22  to the right of    1