Xmpp 功能未实现响应意味着什么

我正在尝试从android应用程序向ejabberd服务器发送一个自定义IQ，我有下面这个类

public class IQCustom extends IQ {


    public final static String childElementName = "query";
    public final static String childElementNamespace = "jabber:iq:conversations";





    public IQCustom(String userFrom, String server)
    {

        super( childElementName, childElementNamespace );
        this.setType(Type.get);


        setTo( server );
        setFrom( userFrom );
    }


    @Override
    protected IQChildElementXmlStringBuilder getIQChildElementBuilder(IQChildElementXmlStringBuilder xml) {




        xml.rightAngleBracket();

        xml.halfOpenElement("abc");
        xml.attribute("op","sum");
        xml.rightAngleBracket();
        xml.closeElement("abc");



        return xml;
    }
}

以下是我得到的智商记录：

    D/SMACK: SENT (1): <iq to=‘example.com' id='BQ8wt-16' type='get'><query xmlns='jabber:iq:conversations'><abc op='sum'></abc></query></iq>
 D/SMACK: RECV (1): <iq to='testing7@example.com/Smack' from='example.com' type='get' id='BQ8wt-16'><query xmlns='jabber:iq:conversations'><abc op='sum'/></query></iq>
 D/SMACK: RECV (1): <r xmlns='urn:xmpp:sm:3'/>
 D/SMACK: SENT (1): <iq to='example.com' id='BQ8wt-16' type='error'><error type='cancel'><feature-not-implemented xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/></error></iq>
 D/SMACK: SENT (1): <r xmlns='urn:xmpp:sm:3'/>
 D/SMACK: SENT (1): <a xmlns='urn:xmpp:sm:3' h='4'/>
 D/SMACK: RECV (1): <a h='5' xmlns='urn:xmpp:sm:3'/>

---

D/SMACK:SENT（1）：你用ns xmpp节实现了这个功能吗？
你的意思是在服务器端我是否有一个插件来处理“jabber:iq:conversations”？好吧，你的评论给了我一个新的思考维度，我发现基本流的示例4解释了我的疑问。这与服务器提供的特性有关，而不是与客户端有关。谢谢。您好@AndreaZedda，经过很多努力和阅读，我仍然不清楚实现该功能意味着什么。我已经编辑了我的问题，将服务器端模块也包括在内。如果有机会，请看一看。
D/SMACK: SENT (1): <iq to='example.com' id='BQ8wt-16' type='error'><error type='cancel'><feature-not-implemented xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/></error></iq>

-module(mod_conversations).
-behaviour(gen_mod).
%% ====================================================================
%% API functions
%% ====================================================================
-export([start/2, stop/1, process_local_iq/3]).
-include("ejabberd.hrl").
-include("logger.hrl").
-include("xmpp.hrl").
-define(NS_IQ_CUSTOM, <<"jabber:iq:conversations">>).
start(Host, _) ->
    gen_iq_handler:add_iq_handler(ejabberd_local, Host, ?NS_IQ_CUSTOM, ?MODULE, process_local_iq, one_queue),
    ?INFO_MSG("Inside mod_conversation",[]),
ok.
stop(Host) ->
    gen_iq_handler:remove_iq_handler(ejabberd_local, Host, ?NS_IQ_CUSTOM),
ok.
process_local_iq(From,_ ,IQ) ->
    From,
    ?INFO_MSG("Inside mod_conversation, IQ is ~p~n ",[IQ]),
    Sum = 2+2,
    IQ.