public static String getRewriterChain(Query query) {
        log(utilsLogger, query, "Retrieving rewriter chain value: " +
            RewriterConstants.REWRITER_CHAIN);

        return getUserParam(query, RewriterConstants.REWRITER_CHAIN);
    }
Get rewriter chain value

@param query Query object from the searcher
@return parameter value or null if not found
container-search/src/main/java/com/yahoo/search/query/rewrite/RewriterUtils.java