What is common to the log and the wall?
The material, both the log and the wall are wooden.
    src         edge_attr  dst
0     0   to the right of    8
1     0   to the right of   10
2     1   to the right of   13
3     2    to the left of   10
4     2    to the left of    8
5     2    to the left of    4
6     2    to the left of   12
7     2    to the left of    6
8     4   to the right of   11
9     4   to the right of    2
10    4  on the bottom of    9
11    6   to the right of    2
12    6   to the right of    8
13    7   to the right of   12
14    8   to the right of    2
15    8    to the left of    0
16    8    to the left of   10
17    8    to the left of    6
18    8   to the right of   11
19   10   to the right of    2
20   10    to the left of    0
21   10   to the right of    8
22   10   to the right of   11
23   11    to the left of   10
24   11    to the left of    8
25   11    to the left of   12
26   11    to the left of    4
27   12                in    9
28   12    to the left of    7
29   12   to the right of    2
30   12   to the right of   11
31   13    to the left of    1