event.setSourceMap(map2);
        assertEquals(2, event.toSource().size());
        assertFalse(event.toSource().containsKey("key1"));
        assertTrue(event.toSource().containsKey("key2"));
        assertTrue(event.toSource().containsKey("key3"));
    }

     */
    Long getVersionNo();

    /**
     * Converts this search log event to a source map for indexing or logging.
     *
     * @return Map representation of the event data
     */
    Map<String, Object> toSource();

    /**
     * Gets the type of this search log event.
     *
     * @return The event type (e.g., "search", "click", "favorite", "user_info")
     */
    String getEventType();

    *
    * @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
    //                                                                              ======
    public abstract Map<String, Object> toSource();

    // ===================================================================================
    //                                                                      Basic Override