`fold:`proceduregraph cycles iterator; every cycle is reprensented as a list of edges. Adjacent edges are adjacent in the list; the cycles are folded together using the user-supplied function

`F`, which is of the form`LAMBDA CYCLE STATE`

`fold:`proceduregraph cycles iterator; every cycle is reprensented as a list of edges. Adjacent edges are adjacent in the list; the cycles are folded together using the user-supplied function

`F`, which is of the form`LAMBDA CYCLE STATE`