How can I ignore and aiortc offer?

Question

I don't know what response I may make in an aiortc offering from browser when I want to ignore it.

async def offer(self,request):  
        params = await request.json()
        offer = RTCSessionDescription(sdp=params["sdp"], type=params["type"])
        if self.reject:#self.reject is True or False defined somewhere above in the code
            #reject offer
            ...
            ...
            ...
            return ????
        else:
            pc = RTCPeerConnection()
            ...
            ...
            ...
            return web.Response(content_type="application/json",text=json.dumps({"sdp": self.pc.localDescription.sdp, "type": self.pc.localDescription.type}))

Edit

If I return an empty sdp for example:

return web.Response(content_type="application/json",text=json.dumps({"sdp": "", "type": ""}))

then where in a JavaScript can I handle this:

function negotiate() {
    return pc.createOffer({offerToReceiveAudio:true}).then(function(offer) {
        return pc.setLocalDescription(offer);
    }).then(function() {
        // wait for ICE gathering to complete
        return new Promise(function(resolve) {
            console.log(pc.iceGatheringState);
            if (pc.iceGatheringState === 'complete') {
                resolve();
            } else {
                function checkState() {
                    console.log(pc.iceGatheringState);
                    if (pc.iceGatheringState === 'complete') {
                        pc.removeEventListener('icegatheringstatechange', checkState);
                        resolve();
                    }
                }
                pc.addEventListener('icegatheringstatechange', checkState);

            }
        });
    }).then(function() {
        var offer = pc.localDescription;
        
        return fetch('/offer', {
            body: JSON.stringify({
                sdp: offer.sdp,
                type: offer.type,
                "name":name,
                "surname":surname
            }),
            headers: {
                'Content-Type': 'application/json'
            },
            method: 'POST'
        });
    }).then(function(response) {
        return response.json();
    }).then(function(answer) {
        return pc.setRemoteDescription(answer);
    }).catch(function(e) {
        alert(e);
        console.log(e);
    });
    
}