What is the boat pulling?
The boat is pulling the ship.
    src        edge_attr  dst
0     0  to the right of   10
1     1   to the left of    2
2     1  to the right of   10
3     1  to the right of    3
4     2  to the right of    4
5     2  to the right of    1
6     2  to the right of   13
7     2  to the right of   10
8     3   to the left of   13
9     3   to the left of    4
10    3   to the left of    1
11    4   to the left of    2
12    4  to the right of    3
13    4  to the right of   10
14    4      coming from   11
15    6           behind    8
16    8           behind   11
17    8               in    7
18    8      in front of    6
19    9   to the left of   12
20    9   to the left of   13
21    9    coming out of   11
22   10        pulled by   11
23   10   to the left of    4
24   10   to the left of    2
25   10   to the left of    1
26   10   to the left of    0
27   10   to the left of   13
28   10   to the left of   11
29   10   to the left of   14
30   11               in    7
31   11          pulling   10
32   11  to the right of   10
33   11      in front of    8
34   12  to the right of    9
35   12               on   13
36   13   to the left of    2
37   13  to the right of    9
38   13  to the right of    3
39   13  to the right of   10
40   14  to the right of   10