Do you see any numbers or letters that are not blue?
No, there are letters but they are blue.
    src        edge_attr  dst
0     0  to the right of    9
1     0  to the right of    6
2     1  to the right of   11
3     1  to the right of    5
4     3  to the right of    9
5     3   to the left of   10
6     5   to the left of    1
7     5   to the left of   13
8     6   to the left of    0
9     6  to the right of    9
10    6  to the right of   12
11    7   to the left of   12
12    7   to the left of   10
13    7  to the right of    9
14    8               in    2
15    9   to the left of   12
16    9   to the left of    6
17    9   to the left of    7
18    9   to the left of    0
19    9   to the left of   10
20    9   to the left of    3
21    9               of    8
22   10  to the right of   12
23   10  to the right of    3
24   10  to the right of    9
25   10  to the right of    7
26   11   to the left of    1
27   11   to the left of   13
28   12   to the left of   10
29   12   to the left of    6
30   12  to the right of    7
31   12  to the right of    9
32   13               of    8
33   13  to the right of    5
34   13  to the right of   11