code: @SuppressWarnings("unchecked")
      private List<ListenerRegistration> addListenerToRegistry() {
          List<ListenerRegistration> registrationsBuilder = newArrayList();
          for (Pair<IdMatcher, Watcher> guiceWatcherRegistration : getRegisteredWatchers()) {
              Watcher watcher = guiceWatcherRegistration.right();
              IdMatcher idMatcher = guiceWatcherRegistration.left();
              Registration registration = registry.addWatcher(idMatcher, watcher);
              ListenerRegistration listenerRegistration = new ListenerRegistration(registration, idMatcher, watcher);
              registrationsBuilder.add(listenerRegistration);
          }
          return registrationsBuilder;
      }
docs: enforce creation of all watcher before register it