Do you see letters in the scene that are not red?
No, there are letters but they are red.
    src        edge_attr  dst
0     1               on    5
1     5           behind    9
2     7  to the right of   11
3     7  to the right of    9
4     9          wearing   11
5     9          holding    8
6     9          wearing   10
7     9      in front of    5
8     9          tossing    6
9     9   to the left of    7
10   11   to the left of    7