private Item buildRegExpSearch(String key, Inspector value) {
        assertHasOperator(key, MATCHES);
        HashMap<Integer, Inspector> children = childMap(value);
        String field = children.get(0).asString();
        String wordData = children.get(1).asString();
        RegExpItem regExp = new RegExpItem(field, true, wordData);
        return leafStyleSettings(getAnnotations(value), regExp);
    }
Translates a list of grouping requests on JSON form to a list in the grouping language form
container-search/src/main/java/com/yahoo/search/query/SelectParser.java