@SuppressWarnings("unchecked")
    public WRITER wrapWriter(Writer writer) {
        return (WRITER)writer;
    }
Wraps the Writer instance.
The result is given as a parameter to all the callback methods.
Must be overridden if the generic parameter WRITER != java.io.Writer.
container-search/src/main/java/com/yahoo/search/rendering/SectionedRenderer.java