Is there a fence that is black?
No, there is a fence but it is red.
   src        edge_attr  dst
0    0   on the edge of    3
1    1  to the right of    2
2    1  to the right of    7
3    1   to the left of    3
4    2   to the left of    1
5    3  to the right of    1
6    5               on    4
7    7   to the left of    1