Is the letter on the post?
Yes, the letter is on the post.
    src        edge_attr  dst
0     0  to the right of    6
1     0   to the left of   14
2     0  to the right of   16
3     0   to the left of   17
4     0  to the right of   11
..  ...              ...  ...
90   18  to the right of    0
91   18  to the right of   14
92   18  to the right of    7
93   18  to the right of   13
94   18   to the left of   15

[95 rows x 3 columns]