What shape are the boxes?
The boxes are round.
    src        edge_attr  dst
0     0   to the left of    4
1     1   to the left of    4
2     2  to the right of   10
3     4  to the right of    8
4     4   to the left of    6
5     4  to the right of    0
6     4  to the right of   12
7     4  to the right of    1
8     6  to the right of    4
9     7   to the left of    9
10    8   to the left of    4
11    9  to the right of    7
12   10   to the left of   13
13   10   to the left of   11
14   10   to the left of    2
15   11  to the right of   10
16   12   to the left of    4
17   13  to the right of   10