code: public void unsubscribe_event(int event_id) throws DevFailed {
  
          //  Get the map
          Hashtable<String, EventCallBackStruct>
                  callBackMap = EventConsumer.getEventCallbackMap();
  
          //  Get the callback structure
          EventCallBackStruct callbackStruct =
                  EventConsumer.getCallBackStruct(callBackMap, event_id);
  
          //  Unsubscribe on EventConsumer object
          if (callbackStruct!=null)
              callbackStruct.consumer.unsubscribe_event(event_id);
      }
docs: ===============================================================