Are there helmets that are not made of metal?
Yes, there is a helmet that is made of plastic.
    src        edge_attr  dst
0     0   to the left of    5
1     1               of   15
2     1  to the right of   16
3     1  to the right of    3
4     1  to the right of   11
5     2   to the left of   23
6     3   to the left of   10
7     3   to the left of   15
8     3   to the left of   13
9     3   to the left of   17
10    3   to the left of    1
11    3   to the left of   16
12    3   to the left of   11
13    5  to the right of   20
14    5  to the right of   21
15    5  to the right of    0
16    5  to the right of    7
17    5  to the right of    8
18    7               of    6
19    7   to the left of    8
20    7   to the left of    5
21    8  to the right of    7
22    8   to the left of    5
23    8               of    6
24    9               on   22
25   10  to the right of   17
26   10  to the right of    3
27   11               of   15
28   11  to the right of    3
29   11   to the left of    1
30   12   to the left of   23
31   13  to the right of   17
32   13   to the left of   23
33   13  to the right of    3
34   15          wearing   10
35   15  to the right of    3
36   15   to the left of   23
37   15  to the right of   17
38   16  to the right of    3
39   16   to the left of    1
40   17               of   16
41   17   to the left of   10
42   17  to the right of    3
43   17   to the left of   15
44   17   to the left of   13
45   20   to the left of   23
46   20   to the left of    5
47   21   to the left of    5
48   23  to the right of   15
49   23  to the right of   20
50   23  to the right of   13
51   23  to the right of    2
52   23  to the right of   12
53   23               on   22