What is the tray made of?
The tray is made of metal.
    src        edge_attr  dst
0     0   to the left of    8
1     0   to the left of    4
2     1   to the left of    4
3     3   to the left of    4
4     4  to the right of    5
5     4  to the right of    3
6     4  to the right of    1
7     4  to the right of    7
8     4  to the right of    0
9     5               on    1
10    5               on    6
11    5   to the left of    4
12    7   to the left of    8
13    7   to the left of    4
14    8  to the right of    0
15    8  to the right of    7