private Set<String> filterValidDocumentTypes(Collection<String> restrict) {
        Set<String> retval = new LinkedHashSet<>();
        for (String docType : restrict) {
            if (docType != null && schema2Searcher.containsKey(docType)) {
                retval.add(docType);
            }
        }
        return retval;
    }
Do not use, for internal testing purposes only. *
container-search/src/main/java/com/yahoo/prelude/cluster/ClusterSearcher.java