public Object insert(Object obj) throws StorageException {
        if(obj instanceof Page) {
            return insert((Page) obj);
        } 
        else if(obj instanceof RobotsTxtHandler.RobotsData) {
            insert((RobotsTxtHandler.RobotsData) obj);
        }
        else if(obj instanceof SitemapXmlHandler.SitemapData) {
            insert((SitemapXmlHandler.SitemapData) obj);
        }
        return null;
    }
This method inserts links from a given page into the frontier

@param obj
           Object - page containing links
@return Object
ache/src/main/java/achecrawler/link/LinkStorage.java