Do you see numbers there that are not white?
Yes, there are black numbers.
    src        edge_attr  dst
0     0  to the right of   11
1     1               on    8
2     1  to the right of    7
3     1   to the left of    3
4     3  to the right of    1
5     3   to the left of   18
6     3  to the right of    7
7     3   to the left of   12
8     3   to the left of   17
9     4   to the left of    5
10    5  to the right of    4
11    7               on   16
12    7   to the left of    8
13    7   to the left of    1
14    7   to the left of   11
15    7   to the left of    3
16    8               on   16
17    8  to the right of    9
18    8  to the right of    7
19    9   to the left of    8
20    9   to the left of   11
21   10   to the left of   14
22   10   to the left of   15
23   11  to the right of    7
24   11  to the right of    9
25   11   to the left of    0
26   12  to the right of    3
27   12  to the right of   18
28   13   to the left of   14
29   14  to the right of   10
30   14  to the right of   13
31   15  to the right of   10
32   17  to the right of    3
33   18   to the left of   12
34   18  to the right of    3