Map<String, Object> parentMap = new LinkedHashMap<>();
        DocMap docMap = new DocMap(parentMap);

        docMap.put("c_key", "value_c");
        docMap.put("a_key", "value_a");
        docMap.put("lang", "en");
        docMap.put("b_key", "value_b");

        Set<Map.Entry<String, Object>> entrySet = docMap.entrySet();