What is the sidewalk made of?
The sidewalk is made of concrete.
    src        edge_attr  dst
0     0  to the right of    2
1     0   to the left of    7
2     1  to the right of    5
3     1             near    4
4     2   to the left of    0
5     2   to the left of    7
6     3  to the right of    5
7     3      in front of    4
8     4           behind    3
9     4  to the right of    5
10    4             near    1
11    5   to the left of    4
12    5  to the right of   11
13    5  to the right of   10
14    5   to the left of    1
15    5   to the left of    3
16    6             near    9
17    7  to the right of    2
18    7  to the right of    0
19    9             near    6
20   10  to the right of   11
21   10   to the left of    5
22   10               at    6
23   10  to the right of   12
24   11   to the left of    5
25   11            above   12
26   11   to the left of   10
27   12            under   11
28   12   to the left of   10