@Override
  protected void enqueueEvent(GatewayQueueEvent<?, ?> event) {
    // @TODO This API hasn't been implemented yet
    throw new UnsupportedOperationException();
  }
Initialize the Executor that handles listener events. Only used by non-primary gateway senders
geode-core/src/main/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderEventProcessor.java