private void updateUserList() {
   List<String> usernames = new ArrayList<>();
   for (Session s : session.getOpenSessions()) {
     String uname = (String) s.getUserProperties().get(USERNAME_KEY);
     usernames.add(uname);
   }
   this.endpointConfig.getUserProperties().put(USERNAMES_KEY, usernames);
 }
 public void resetTweets() {
   tweets.removeAll(tweets);
 }