What is common to the number and the parking sign?
The color, both the number and the parking sign are white.
    src        edge_attr  dst
0     0  to the right of    1
1     1  to the right of    6
2     1   to the left of    0
3     1  to the right of    5
4     1   to the left of    2
5     2  to the right of    1
6     3  to the right of    5
7     4               on    3
8     4  to the right of    5
9     4  to the right of    6
10    5   to the left of    4
11    5   to the left of    3
12    5   to the left of    1
13    6   to the left of    4
14    6   to the left of    1