in workflow.go [210:220]
func (w *Workflow) UpstreamOf(step Steper) map[Steper]StepResult {
if w.Empty() {
return nil
}
rv := make(map[Steper]StepResult)
for up := range w.StateOf(step).Upstreams() {
up = w.RootOf(up)
rv[up] = w.StateOf(up).GetStepResult()
}
return rv
}