Getting all tags in a historical tag provider

Module Development
1

How do I get all tags in the tag history provider?

    @Override
    public void setup(GatewayContext gatewayContext) {
        this.context = gatewayContext;

        try {
            GatewayTagHistoryManager tagHistoryManager = context.getTagHistoryManager();
            TagHistoryProvider tagHistoryProvider = tagHistoryManager.getTagHistoryProvider("Test Provider");

            if (tagHistoryProvider != null) {
                Date startDate = new Date(System.currentTimeMillis() - 86400000); // 24 hours ago
                Date endDate = new Date();                
                //what should I do here?
                //tagHistoryProvider.queryDensity();
            } else {
                logger.error("Tag History Provider not found.");
            }
        } catch (Exception e) {
            logger.error("Error while accessing Tag History Provider.", e);
        }
    }