What is the color of the walls?
The walls are white.
    src        edge_attr  dst
0     0   to the left of   10
1     0   to the left of   11
2     2  to the right of    4
3     4   to the left of    8
4     4   to the left of    6
5     4   to the left of    2
6     5   to the left of   10
7     5   to the left of   11
8     6  to the right of    4
9     8  to the right of    4
10   10  to the right of    5
11   10  to the right of    0
12   11  to the right of    5
13   11  to the right of    0