What is that envelope on?
The envelope is on the platter.
    src        edge_attr  dst
0     0               on    3
1     0   to the left of    6
2     0   to the left of    1
3     1   to the left of    6
4     1  to the right of    0
5     1  to the right of    7
6     3   to the left of    6
7     3               on    2
8     6  to the right of    0
9     6  to the right of    3
10    6  to the right of    1
11    7               on    3
12    7   to the left of    1