if (!ImapFolder.isFolderVisible(folder))
if (!ImapFolder.isFolderVisible(folder, (ImapSession) mSession))
    protected void callback() throws ServiceException {        synchronized (mMailbox) {            Folder folder = mMailbox.getFolderByPath(this.getOpCtxt(), mFolderName);            if (!ImapFolder.isFolderVisible(folder))                throw ImapServiceException.FOLDER_NOT_VISIBLE(mFolderName);            if (!folder.isTagged(mMailbox.mSubscribeFlag))                mMailbox.alterTag(mOpCtxt, folder.getId(), MailItem.TYPE_FOLDER, Flag.ID_FLAG_SUBSCRIBED, true);        }    }