What is the sign on?
The sign is on the tree.
    src        edge_attr  dst
0     0               of   14
1     0  to the right of   11
2     0  to the right of    6
3     0  to the right of   12
4     0  to the right of   10
..  ...              ...  ...
56   15   to the left of   12
57   15   to the left of    1
58   15   to the left of    4
59   15   to the left of   14
60   15               on    7

[61 rows x 3 columns]