What's in front of the tree?
The bus is in front of the tree.
    src        edge_attr  dst
0     0   to the left of    1
1     0   to the left of    9
2     0               in   15
3     0  to the right of   11
4     0  to the right of    6
..  ...              ...  ...
57   18  to the right of    8
58   18  to the right of   15
59   18  to the right of    9
60   18  to the right of    1
61   18           beside    9

[62 rows x 3 columns]