What color is the clear sky behind the building?
The sky is light blue.
    src        edge_attr  dst
0     0      in front of    4
1     0           behind    6
2     0     reflected on    0
3     0           behind    3
4     1  to the right of    5
5     3  to the right of    6
6     3      in front of    0
7     3  to the right of    5
8     4           behind    0
9     5   to the left of    3
10    5   to the left of    1
11    6      in front of    0
12    6   to the left of    3