Are there either trucks or airplanes that are green?
Yes, the airplane is green.
   src        edge_attr  dst
0    2   to the left of    3
1    3  to the right of    2
2    6               of    4
3    6  to the right of    8
4    6  to the right of    7
5    7   to the left of    6
6    8   to the left of    6