code: public <T extends EventObject> void setDefaultEventCallback(
              final CrawlEvent event,
              final Consumer<T> callback) {
          defaultCallbacks.put(event, callback);
      }
docs: Sets the default callback for the specific event.
  
  @param <T>      the type of the input to the operation
  @param event    the event for which the callback should be invoked
  @param callback the operation to be performed