What is the green tray made of?
The tray is made of plastic.
    src        edge_attr  dst
0     1  to the right of    3
1     2  to the right of    4
2     2  to the right of    5
3     2  to the right of    6
4     2  to the right of    7
5     3  to the right of    5
6     3   to the left of    1
7     4   to the left of    2
8     4  to the right of    6
9     5   to the left of    2
10    5   to the left of    3
11    6   to the left of    2
12    6   to the left of    4
13    7   to the left of    2