Which kind of sign is in front of the sky?
The sign is a stop sign.
    src        edge_attr  dst
0     0  to the right of    4
1     0               on    1
2     0  to the right of    2
3     1      in front of    8
4     2   to the left of    4
5     2   to the left of    0
6     2               on    1
7     4   to the left of    0
8     4               on    1
9     4  to the right of    2
10    5  to the right of    8
11    5        on top of    7
12    6               on    5
13    6  to the right of    8
14    8   to the left of    5
15    8   to the left of    6
16    8           behind    1