code: public void consumer(Class<?> api,
                          @Pin ServiceRefAmp serviceRef,
                          Result<? super Cancel> result)
    {
      String path = api.getName();
        
      String address = address(path);
        
      EventNodeAsset node = lookupPubSubNode(address);
        
      Cancel cancel = node.consumeImpl(serviceRef);
        
      result.ok(cancel);
    }
docs: Consume a callback to a location.