code: @Reference(cardinality = ReferenceCardinality.MULTIPLE,
                 policy = ReferencePolicy.DYNAMIC)
      protected void setOsgiEventHandler(ServiceReference<org.osgi.service.event.EventHandler> handlerReference) {
          topicCache.addHandler(handlerReference, true);
      }
docs: Inject a ServiceReference to a service that implements the OSGi <code>EventHandler</code> interface.
  
  @param handlerReference
  the service reference