Are there letters that are not black?
Yes, there are white letters.
     src        edge_attr  dst
0      0  to the right of   13
1      0  to the right of   16
2      0  to the right of   15
3      0  to the right of    1
4      0   to the left of   20
..   ...              ...  ...
113   25  to the right of    5
114   25  to the right of    7
115   25  to the right of   21
116   25  to the right of    1
117   25               on   23

[118 rows x 3 columns]