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