What is on the wall?
The pipe is on the wall.
    src        edge_attr  dst
0     1               on    4
1     1  to the right of    6
2     1  to the right of    2
3     1  to the right of    3
4     2   to the left of    5
5     2   to the left of    3
6     2   to the left of    4
7     2   to the left of    1
8     2   to the left of    7
9     2   to the left of    6
10    2   to the left of    8
11    3   to the left of    1
12    3  to the right of    2
13    4  to the right of    2
14    5  to the right of    2
15    6   to the left of    1
16    6  to the right of    2
17    6               in    3
18    7  to the right of    2
19    8  to the right of    2