What is the ladder made of?
The ladder is made of metal.
   src        edge_attr  dst
0    1               in    9
1    1               in    2
2    3  to the right of    4
3    4   to the left of    3
4    5  to the right of    6
5    6   to the left of    7
6    6   to the left of   10
7    6   to the left of    5
8    7  to the right of    6
9   10  to the right of    6