What does the moss grow on?
The moss grows on the tree.
    src        edge_attr  dst
0     0  to the right of   12
1     0  to the right of   13
2     0  to the right of    3
3     0  to the right of    2
4     2               on    1
5     2  to the right of    7
6     2   to the left of    0
7     2  to the right of   11
8     2   to the left of   10
9     2   to the left of   13
10    3       sitting on    1
11    3   to the left of   10
12    3   to the left of    0
13    3  to the right of   11
14    3        parked on    1
15    4   on the back of    5
16    5   to the left of   11
17    6  to the right of   11
18    7   to the left of   12
19    7   to the left of   13
20    7   to the left of    2
21    9           around    0
22   10       growing on    0
23   10  to the right of    3
24   10  to the right of    2
25   10  to the right of   12
26   11  to the right of    5
27   11   to the left of    6
28   11   to the left of    2
29   11   to the left of    3
30   11   to the left of   12
31   12  to the right of   11
32   12  to the right of    7
33   12   to the left of   10
34   12   to the left of    0
35   13   to the left of    0
36   13  to the right of    7
37   13  to the right of    2