What's in front of the fence?
The rocks are in front of the fence.
    src        edge_attr  dst
0     1   to the left of   13
1     2   to the left of   20
2     2   to the left of    5
3     2  to the right of    4
4     2   to the left of   11
..  ...              ...  ...
56   20  to the right of    2
57   20  to the right of    4
58   20  to the right of   16
59   20  to the right of    7
60   21           behind    3

[61 rows x 3 columns]