What is on the bridge?
The gate is on the bridge.
    src        edge_attr  dst
0     0  to the right of    1
1     1   to the left of    0
2     2   to the left of   14
3     2  to the right of    8
4     3               on   18
5     4   to the left of    9
6     6               in   12
7     6  to the right of   19
8     6   to the left of   17
9     6   to the left of   11
10    8   to the left of   14
11    8   to the left of    2
12    9  to the right of    4
13   10             near   11
14   11             near   10
15   11  to the right of    6
16   13  to the right of   18
17   14  to the right of    8
18   14  to the right of    2
19   17  to the right of    6
20   18   to the left of   13
21   19               in   12
22   19   to the left of    6