Which side of the image is the shelf on?
The shelf is on the left of the image.
    src        edge_attr  dst
0     0   to the left of   11
1     0   to the left of    7
2     0   to the left of   12
3     1  to the right of   12
4     1  to the right of   11
5     1   to the left of    3
6     3  to the right of   12
7     3  to the right of    5
8     3  to the right of    1
9     3  to the right of    9
10    3  to the right of    7
11    5   to the left of    3
12    7   to the left of    3
13    7  to the right of    0
14    8               on    7
15    9   to the left of    3
16   11  to the right of    0
17   11   to the left of    1
18   12   to the left of    3
19   12   to the left of    1
20   12  to the right of    0