What is on the bridge made out of metal?
The bus is on the bridge.
    src        edge_attr  dst
0     0               on    6
1     0   to the left of    7
2     0  to the right of    2
3     0   to the left of   10
4     0  to the right of    8
5     1   to the left of    5
6     1               on    2
7     2            above    8
8     2            above    7
9     2            above    9
10    2   to the left of    5
11    2   to the left of    6
12    2   to the left of    7
13    2   to the left of   10
14    2   to the left of    3
15    2   to the left of    0
16    3  to the right of    8
17    3  to the right of    2
18    5  to the right of    1
19    5  to the right of    2
20    5  to the right of    8
21    5   to the left of   10
22    5   to the left of   13
23    5   to the left of    7
24    6  to the right of    8
25    6   to the left of    7
26    6  to the right of    2
27    6   to the left of   10
28    7            under    2
29    7  to the right of    6
30    7  to the right of    5
31    7  to the right of    2
32    7  to the right of    0
33    8               by   11
34    8   to the left of    3
35    8   to the left of    0
36    8   to the left of    5
37    8   to the left of    6
38    9            under    2
39   10  to the right of    5
40   10  to the right of    6
41   10  to the right of    0
42   10  to the right of    2
43   12               of    8
44   13  to the right of    5