What is on the shelf?
The towels are on the shelf.
    src        edge_attr  dst
0     0   to the left of    6
1     1               on   14
2     1  to the right of   18
3     1  to the right of   17
4     2               on   10
5     2  to the right of   12
6     5               on   15
7     6               on   10
8     6  to the right of    0
9     7   to the left of   11
10    7               on   15
11    9   to the left of   12
12    9  to the right of   13
13    9  to the right of   19
14   11  to the right of    7
15   11  to the right of   15
16   12   to the left of    2
17   12  to the right of   13
18   12  to the right of    9
19   12  to the right of   19
20   13   to the left of    9
21   13  to the right of   19
22   13   to the left of   12
23   15   to the left of   11
24   16               on   15
25   17   to the left of    1
26   17               on   14
27   18   to the left of    1
28   19   to the left of   12
29   19   to the left of    9
30   19   to the left of   13