What type of material is the lid made of?
The lid is made of metal.
    src         edge_attr  dst
0     0    to the left of    7
1     0   to the right of   16
2     0    to the left of   11
3     0   to the right of    6
4     0   to the right of   12
5     0    to the left of   13
6     2  on the bottom of    5
7     2   to the right of   12
8     3   to the right of   12
9     3   to the right of   16
10    3    to the left of   13
11    5   to the right of    6
12    5   to the right of   12
13    6    to the left of    0
14    6    to the left of    5
15    6    to the left of   10
16    7   to the right of    0
17    8    to the left of   15
18    9   to the right of   12
19    9   to the right of   16
20   10   to the right of   12
21   10   to the right of    6
22   11   to the right of    0
23   12    to the left of    9
24   12    to the left of    0
25   12    to the left of    2
26   12    to the left of   10
27   12    to the left of   16
28   12    to the left of    5
29   12    to the left of    3
30   13   to the right of    3
31   13   to the right of    0
32   15   to the right of    8
33   15   to the right of   16
34   16    to the left of    9
35   16    to the left of   15
36   16    to the left of    0
37   16    to the left of    3
38   16   to the right of   12