default void initializeState(FunctionInitializationContext context) {
        // no initialization needed
    }
Process the incoming element to produce multiple ActionsRequests. The
produced requests should be added to the provided {@link RequestIndexer}.

@param element incoming element to process
@param ctx runtime context containing information about the sink instance
@param indexer request indexer that {@code ActionRequest} should be added to
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/elasticsearch-base/src/main/java/org/apache/inlong/sort/elasticsearch/ElasticsearchSinkFunction.java