AP pipeline want to have order of visit processing processing to be stable, in particular association steps for one visit needs to wait until the same step for previous visit is finished. Adding this sort of dependency for quantum graph would be difficult. It may be easier to implement special scheduling logic while executing the graph instead. I want to explore how this can be done in current pipetask and try to make it scheduling more configurable/extensible. Some refactoring (that we always wanted to do) of the internals will probably be needed.