What is used to make the bridge?
The bridge is made of wood.
    src        edge_attr  dst
0     0  to the right of   13
1     0  to the right of    4
2     0  to the right of    1
3     0  to the right of   11
4     0  to the right of    9
..  ...              ...  ...
63   14   to the left of    7
64   15   to the left of    5
65   16   to the left of    7
66   16   to the left of    9
67   16   to the left of   13

[68 rows x 3 columns]