What is covered with trees?
The mountain is covered with trees.
    src        edge_attr  dst
0     1   to the left of    8
1     2      attached to   10
2     3               in    0
3     3  to the right of    9
4     3   to the left of    8
5     4   to the left of   12
6     4   to the left of    8
7     5  to the right of    9
8     5   to the left of    8
9     5   to the left of   12
10    5   to the left of    7
11    7  to the right of    5
12    8  to the right of   11
13    8  to the right of    1
14    8  to the right of    3
15    8  to the right of    4
16    8  to the right of    5
17    8  to the right of    9
18    9   to the left of    8
19    9   to the left of    3
20    9   to the left of    5
21   10  to the right of   11
22   11   to the left of   10
23   11   to the left of    8
24   12     covered with    8
25   12  to the right of    5
26   12  to the right of    4