Which place is it?
It is a harbor.
   src        edge_attr  dst
0    5   to the left of   12
1    6  to the right of    8
2    8   to the left of    6
3   10   to the left of   12
4   11  to the right of   12
5   12  to the right of    5
6   12  to the right of   10
7   12   to the left of   11