What is the color of the trees?
The trees are green.
    src        edge_attr  dst
0     0               by    1
1     0  to the right of    1
2     0   to the left of    3
3     1   to the left of    6
4     1   to the left of    0
5     3  to the right of    6
6     3  to the right of    4
7     3  to the right of    0
8     3  to the right of    5
9     4   to the left of    3
10    5   to the left of    3
11    6  to the right of    1
12    6   to the left of    3