Who rides the bike?
The couple rides a bike.
    src        edge_attr  dst
0     0           riding    3
1     0  to the right of    1
2     1   to the left of    4
3     1   to the left of    9
4     1   to the left of    8
5     1   to the left of    2
6     1   to the left of    0
7     2  to the right of    5
8     2  to the right of    1
9     4  to the right of    1
10    5   to the left of    2
11    5   to the left of    6
12    6  to the right of    5
13    7               on   10
14    8               on    3
15    8  to the right of    1
16    9  to the right of   11
17    9  to the right of    1
18   11   to the left of    9