code: public DuzztState getSuccessor(DuzztAction action) {
  		DuzztTransition t = getTransition(action);
  		if(t == null) {
  			return null;
  		}
  		return t.getSuccessor();
  	}
docs: Retrieves the successor state reached via a given action. If no transition
  is triggered by this action, <tt>null</tt> is returned.
  @param action the action
  @return the successor state reached via the specified action, or <tt>null</tt>