What color is the clock on the wall?
The clock is black.
   src        edge_attr  dst
0    0  to the right of    3
1    2               of    3
2    2   to the left of    5
3    3               on    0
4    3               on    6
5    3   to the left of    0
6    3               on    4
7    5  to the right of    2