What is the fence around of?
The fence is around the planes.
    src        edge_attr  dst
0     0  to the right of   11
1     0  to the right of   10
2     1           behind    6
3     1           behind    3
4     1           behind   16
..  ...              ...  ...
95   23   to the left of    9
96   23  to the right of   15
97   24  to the right of    9
98   24  to the right of   20
99   24  to the right of   23

[100 rows x 3 columns]