What is the sidewalk made of?
The sidewalk is made of wood.
   src        edge_attr  dst
0    0   to the left of    2
1    0   to the left of    5
2    0   to the left of    3
3    2  to the right of    0
4    3               of    2
5    3  to the right of    0
6    5  to the right of    0