What is the sidewalk made of?
The sidewalk is made of brick.
    src        edge_attr  dst
0     2  to the right of   11
1     2  to the right of    5
2     2   to the left of    4
3     2   to the left of    7
4     3  to the right of    9
5     3  to the right of    8
6     3   to the left of   10
7     3               on    9
8     4  to the right of    2
9     4  to the right of    6
10    4  to the right of    5
11    4  to the right of   11
12    5   to the left of    2
13    5   to the left of    4
14    6   to the left of    4
15    6  to the right of   11
16    7  to the right of   10
17    7  to the right of    2
18    8   to the left of    3
19    8       walking on    9
20    8   to the left of   11
21    9   to the left of    3
22   10  to the right of    3
23   10   to the left of    7
24   10  to the right of   11
25   11   to the left of    2
26   11   to the left of   10
27   11   to the left of    6
28   11  to the right of    8
29   11   to the left of    4