Do you see wire cages or fences?
Yes, there is a wire fence.
    src        edge_attr  dst
0     0  to the right of   15
1     1   to the left of   11
2     3  to the right of   17
3     4  to the right of    7
4     4   to the left of    6
5     4               by    6
6     4               by    7
7     5   to the left of   10
8     5   to the left of   11
9     6  to the right of    4
10    7   to the left of    4
11   10  to the right of    5
12   11  to the right of    5
13   11  to the right of    1
14   12   to the left of   16
15   15   to the left of    0
16   16  to the right of   12
17   17   to the left of    3