What material is used to make the side walk?
The side walk is made of wood.
    src        edge_attr  dst
0     0   to the left of    7
1     0   to the left of    6
2     0  to the right of    8
3     0           behind    7
4     1   to the left of   10
..  ...              ...  ...
63   13   to the left of    9
64   13   to the left of   10
65   13   to the left of    6
66   13   to the left of    3
67   14   to the left of    1

[68 rows x 3 columns]