How clean is the sky that looks blue?
The sky is clean.
   src        edge_attr  dst
0    3  to the right of    8
1    4   to the left of    8
2    4   to the left of    9
3    5  to the right of    9
4    7            above    9
5    8  to the right of    4
6    8   to the left of    3
7    9               on    8
8    9   to the left of    5
9    9  to the right of    4