What is the bridge made of?
The bridge is made of metal.
    src        edge_attr  dst
0     0   to the left of    4
1     0               in    1
2     0   to the left of    5
3     2   to the left of    7
4     2           behind    5
5     3   to the left of    5
6     3   to the left of   14
7     4   to the left of   11
8     4  to the right of    0
9     5  to the right of    8
10    5   to the left of   11
11    5  to the right of    3
12    5      in front of    2
13    5  to the right of    0
14    5   to the left of   12
15    5   to the left of    9
16    5   to the left of    6
17    6  to the right of    5
18    6   to the left of    7
19    6   to the left of   13
20    7  to the right of    2
21    7  to the right of    6
22    8   to the left of    5
23    8   to the left of   14
24    9  to the right of    5
25   10   to the left of   13
26   11  to the right of    4
27   11  to the right of    5
28   12  to the right of    5
29   13  to the right of   10
30   13  to the right of    6
31   14  to the right of    3
32   14  to the right of    8