code: public void addNamespace(final MongoNamespace namespace) {
      this.instanceLock.writeLock().lock();
      try {
        if (this.nsStreamers.containsKey(namespace)) {
          return;
        }
        final NamespaceChangeStreamListener streamer =
            new NamespaceChangeStreamListener(
                namespace,
                instanceConfig.getNamespaceConfig(namespace),
                service,
                networkMonitor,
                authMonitor,
                getLockForNamespace(namespace));
        this.nsStreamers.put(namespace, streamer);
      } finally {
        this.instanceLock.writeLock().unlock();
      }
    }
docs: Requests that the given namespace be started listening to for change events.
  
  @param namespace the namespace to listen for change events on.