public String getActionType(Instance vision) throws Exception {
		
        // Set default action type to Turn.
		double action = actionNumMap.get("turn"); 
		// Make the decision on action type by model.
		try {
			action = actionTypeCls.classifyInstance(vision);
		} catch (Exception e) {
			System.err.println("Cannot make the decision on action type.");
			e.printStackTrace();
		}
		
		String result = null;
		for (Iterator<?> iter = actionNumMap.entrySet().iterator(); iter.hasNext();) {
			@SuppressWarnings("rawtypes")
			Map.Entry entry = (Entry) iter.next();
			if ((Double)entry.getValue() == action)
				result = (String) entry.getKey();
		}
		
		// return action name
        return result; 
	}