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