What is the color of the shelf made of wood?
The shelf is brown.
    src        edge_attr  dst
0     0   to the left of   15
1     0  to the right of   10
2     1  to the right of    9
3     1   to the left of    4
4     2               of    1
5     2  to the right of    9
6     2   to the left of    4
7     3   to the left of    5
8     4  to the right of    2
9     4  to the right of    1
10    4  to the right of    9
11    5  to the right of    3
12    5  to the right of   10
13    7               on   14
14    8               in   10
15    9   to the left of    1
16    9   to the left of    2
17    9   to the left of    4
18   10   to the left of    0
19   10   to the left of    5
20   11   to the left of   12
21   11               of   14
22   12  to the right of   11
23   12  to the right of   14
24   14   to the left of   12
25   15  to the right of    0