What is this, a truck or a bus?
This is a truck.
    src        edge_attr  dst
0     1   to the left of    6
1     1  to the right of   10
2     3  to the right of    4
3     4   to the left of    3
4     4   to the left of    7
5     6  to the right of   13
6     6  to the right of   12
7     6  to the right of    1
8     7  to the right of    4
9     7   to the left of   15
10   10   to the left of    1
11   10   to the left of   13
12   11   to the left of   15
13   12   to the left of    6
14   12   to the left of   15
15   12               of    8
16   13  to the right of   10
17   13   to the left of    6
18   15  to the right of    7
19   15  to the right of   12
20   15  to the right of   11