public void handle(Event event) {
        S state = stateHolder.getState();
        try {
            handle(event, sinkHandlerCallback, state);
        } finally {
            stateHolder.returnState(state);
        }
    }
SinkHandler is an optional interface before {@link SinkMapper}.
It will do optional processing to the events before sending the events to the desired mapper

@param <S> current state for the Sink Holder
modules/siddhi-core/src/main/java/io/siddhi/core/stream/output/sink/SinkHandler.java