/// <summary>
        /// Sends a RemoveBookmarksMessage to remove the given bookmark from the server.
        /// https://xmpp.org/extensions/xep-0402.html#removing-a-bookmark
        /// </summary>
        /// <param name="conferenceItem">The bookmark that should get removed from the server.</param>
        /// <param name="onMessage">The method that should get executed once the helper receives a new valid message (can be null).</param>
        /// <param name="onTimeout">The method that should get executed once the helper timeout gets triggered (can be null).</param>
        /// <returns>Returns a MessageResponseHelper listening for RemoveBookmarksMessage answers.</returns>
        public MessageResponseHelper <IQMessage> removeBookmark_xep_0402(ConferenceItem conferenceItem, MessageResponseHelper <IQMessage> .OnMessageHandler onMessage, MessageResponseHelper <IQMessage> .OnTimeoutHandler onTimeout)
        {
            MessageResponseHelper <IQMessage> helper = new MessageResponseHelper <IQMessage>(CONNECTION, onMessage, onTimeout);
            RemoveBookmarkMessage             msg    = new RemoveBookmarkMessage(CONNECTION.account.getFullJid(), conferenceItem);

            helper.start(msg);
            return(helper);
        }
        /// <summary>
        /// Sends a RemoveBookmarksMessage for removing the given bookmark from the server.
        /// https://xmpp.org/extensions/xep-0402.html#removing-a-bookmark
        /// </summary>
        /// <param name="conferenceItem">The bookmark that should get removed from the server.</param>
        /// <param name="onMessage">The method that should get executed once the helper receives a new valid message (can be null).</param>
        /// <param name="onTimeout">The method that should get executed once the helper timeout gets triggered (can be null).</param>
        /// <returns>Returns a MessageResponseHelper listening for RemoveBookmarksMessage answers.</returns>
        public MessageResponseHelper <IQMessage> removeBookmark_xep_0402(ConferenceItem conferenceItem, Func <IQMessage, bool> onMessage, Action onTimeout)
        {
            MessageResponseHelper <IQMessage> helper = new MessageResponseHelper <IQMessage>(CLIENT, onMessage, onTimeout);
            RemoveBookmarkMessage             msg    = new RemoveBookmarkMessage(CLIENT.getXMPPAccount().getIdDomainAndResource(), conferenceItem);

            helper.start(msg);
            return(helper);
        }