What sign is stacked?
The sign is a street sign.
    src        edge_attr  dst
0     2   to the left of    3
1     2   to the left of    5
2     3  to the right of    2
3     3  to the right of    8
4     4            above    9
5     4  to the right of    7
6     4  to the right of    6
7     5  to the right of    8
8     5  to the right of    2
9     6               on    7
10    6   to the left of    4
11    7   to the left of    4
12    8   to the left of    5
13    8   to the left of    3
14    9            below    4