how to use before-preview-change

[impronta48]

I've tried this

 <v-md-editor id="md-editor" v-model="text" class="w-100 h-100" @save="saveMd()" :before-preview-change="beforePreviewChange(text, aq)"></v-md-editor>

And in my methods

        beforePreviewChange(text, next) {
            console.log("text", text);            
            return next(text);
        },
        aq(text) {
            console.log("NEXXT")
            text = "TEXT";
            return "text";
        }

but I can't modify the preview text (I need to add absolute URLs to images).
Can you provide an example?
Thanks