What's in front of the fence?
The leaves are in front of the fence.
   src        edge_attr  dst
0    0           behind    3
1    0   to the left of    2
2    2  to the right of    0
3    2  to the right of    8
4    3      in front of    0
5    4  to the right of    9
6    8   to the left of    2
7    9   to the left of    4