What are the leaves on?
The leaves are on the trees.
    src        edge_attr  dst
0     0        parked on    9
1     0  to the right of    5
2     0  to the right of    8
3     0  to the right of    6
4     1        parked on    9
5     1               on    9
6     1  to the right of   13
7     1  to the right of   10
8     1   to the left of    6
9     1   to the left of    5
10    1  to the right of   14
11    1   to the left of    8
12    1  to the right of    7
13    2   to the left of    3
14    3               on    2
15    3  to the right of    2
16    5  to the right of    1
17    5   to the left of    0
18    6  to the right of    1
19    6   to the left of    0
20    6               on    8
21    7   to the left of    1
22    7   to the left of   11
23    7        parked on    9
24    7               on    9
25    8        parked on    9
26    8   to the left of    0
27    8  to the right of    1
28    8  to the right of   11
29   10   to the left of    1
30   10               on    7
31   11               on    1
32   11  to the right of    7
33   11   to the left of    8
34   12               in    4
35   13   to the left of    1
36   14   to the left of    1
37   14  on the front of    7