public void setUsers(UserCollection users) {
   users.addObserver(this);
   this.users = users;
   notifyDataSetChanged();
   for (int i = 0; i < getGroupCount(); i++) {
     list.expandGroup(i);
   }
 }
 @Override
 public Pair<IrcMode, List<IrcUser>> getGroup(int groupPosition) {
   int counter = 0;
   for (IrcMode mode : IrcMode.values()) {
     if (counter == groupPosition) {
       return new Pair<IrcMode, List<IrcUser>>(mode, users.getUniqueUsersWithMode(mode));
     } else {
       counter++;
     }
   }
   return null;
 }
 public void stopObserving() {
   if (users != null) users.deleteObserver(this);
 }