code: function _observeSubscriptionSyncEvents(args) {
    var rtm = args.rtm;
    var filterFn = args.filterFn;
  
    rtm.on('subscription-created', function(subscription) {
      if (subscription.allowRead !== true) return;
  
      filterFn(subscription).then(function(ok) {
        if (ok) {
          rtm.subscribe({channel: subscription.channelId});
        }
      });
    });
  
    rtm.on('subscription-deleted', function(subscription) {
      rtm.unsubscribe({channel: subscription.channelId});
    });
  
    rtm.on('subscription-updated', function(subscription) {
      if (subscription.allowRead === false) {
        return rtm.unsubscribe({channel: subscription.channelId});
      }
      filterFn(subscription).then(function(ok) {
        if (ok) {
          rtm.subscribe({channel: subscription.channelId});
        }
      });
    });
  }
docs: Register event listeners for keeping subscriptions in sync.
  
  @param {Object} args
  @param {RtmClient} args.rtm
  @param {Function} args.filterFn
  @private