code: private <TEvent> void unimplemented(final long identifier, final TEvent event) {
      LOG.log(Level.SEVERE, "Unimplemented event: [{0}]: {1}", new Object[] {identifier, event});
      throw new RuntimeException("Event not supported: " + event);
    }
docs: Called when an event is received that does not have an onNext method definition
  in TSubCls. Override in TSubClas to handle the error.
  @param event A reference to an object which is an event not handled by TSubCls.
  @param <TEvent> The type of the event being processed.