What animal is on top of the gravel?
The horse is on top of the gravel.
    src        edge_attr  dst
0     2   to the left of   11
1     4               on   12
2     4   to the left of   15
3     4        on top of   19
4     4        on top of   12
5     5  to the right of    7
6     5  to the right of   17
7     5  to the right of   18
8     6   to the left of   15
9     6  to the right of   11
10    7  to the right of    8
11    7   to the left of    5
12    7   to the left of   15
13    8   to the left of   18
14    8   to the left of   17
15    8   to the left of   15
16    8   to the left of    7
17    9   to the left of   18
18    9   to the left of   17
19   11   to the left of    6
20   11  to the right of    2
21   11   to the left of   16
22   14   to the left of   15
23   15  to the right of   17
24   15  to the right of   14
25   15  to the right of    8
26   15  to the right of    7
27   15  to the right of    6
28   15  to the right of    4
29   15  to the right of   18
30   16  to the right of   11
31   17          wearing    6
32   17   to the left of   15
33   17          wearing   16
34   17        on top of    4
35   17  to the right of    8
36   17  to the right of    9
37   17          wearing    7
38   17        riding on    4
39   17   to the left of    5
40   18   to the left of    5
41   18  to the right of    9
42   18  to the right of    8
43   18   to the left of   15