code: @Override
      public void unsubscribe(String channel, ISubscriber<ID, DATA> subscriber) {
          try {
              WrapAroundSubscriber wrap = subscriptions.get(channel).getIfPresent(subscriber);
              if (wrap != null) {
                  eventBus.get(channel).unregister(wrap);
              }
          } catch (ExecutionException e) {
              throw new RuntimeException(e);
          }
      }
docs: {@inheritDoc}