What are the traffic lights hanging from?
The traffic lights are hanging from the wires.
   src        edge_attr  dst
0    0     hanging from    1
1    0   to the left of    6
2    2   to the left of    6
3    3   to the left of    6
4    4               of    3
5    4   to the left of    6
6    6  to the right of    0
7    6  to the right of    2
8    6  to the right of    4
9    6  to the right of    3