The trees are what color?
The trees are green.
    src        edge_attr  dst
0     4   to the left of   16
1     4   to the left of   13
2     5  to the right of   16
3     5               in    2
4     6               in    2
5     8               in    2
6     9  to the right of   14
7     9  to the right of   17
8     9   to the left of   15
9    12               of   15
10   13  to the right of    4
11   13               in    2
12   14   to the left of    9
13   14   to the left of   17
14   15  to the right of    9
15   15  to the right of   19
16   16  to the right of    4
17   16   to the left of    5
18   17   to the left of    9
19   17  to the right of   14
20   18               of   11
21   19   to the left of   15