What are these shelves made of?
The shelves are made of wood.
     src        edge_attr  dst
0      0   to the left of   16
1      0   to the left of    9
2      0   to the left of   17
3      0   to the left of   15
4      0   to the left of   13
..   ...              ...  ...
118   24  to the right of   17
119   24   to the left of    5
120   24   to the left of   23
121   24  to the right of   13
122   24  to the right of    8

[123 rows x 3 columns]