Are there both mailboxes and bridges in this image?
No, there is a bridge but no mailboxes.
   src        edge_attr  dst
0    3      floating in    2
1    4  to the right of    8
2    4   to the left of   11
3    8   to the left of    4
4    8   to the left of    9
5    9   to the left of   11
6    9          wearing    4
7    9  to the right of    8
8   11  to the right of    4
9   11  to the right of    9