public Vector<Transition> getTransitions(Box beforeRootBox, Box afterRootBox) {
// Ensure that beforeRootBox and afterRootBox have been set.
Vector<Transition> transitions = new Vector<Transition>();
for (Step step : steps) {
Transition t = step.getTransition(beforeRootBox, afterRootBox);
if (t!=null) {
transitions.add(t);
}
}
return transitions;