Map<String, Object> nested = new HashMap<>();
        nested.put("NestedKey", "nestedValue");
        source.put("NestedMap", nested);

        Map<String, Object> result = searchLogHelper.toLowerHyphen(source);

        assertEquals("value1", result.get("test_key"));
        assertEquals("value2", result.get("another_test_key"));

        @SuppressWarnings("unchecked")

    *
    * @param searchLogEvent The search log event.
    * @return The source map.
    */
    protected Map<String, Object> toSource(final SearchLogEvent searchLogEvent) {
        final Map<String, Object> source = toLowerHyphen(searchLogEvent.toSource());
        source.put("_id", searchLogEvent.getId());
        // source.put("version_no", searchLogEvent.getVersionNo());
        source.put("event_type", searchLogEvent.getEventType());