docs: function(subscriptionType){
      var curSubscriptionType = this.subscribeTo;
      var newSubscriptionType = subscriptionType & SUBSCRIPTION.ALL;
      var delta = curSubscriptionType ^ newSubscriptionType;
  
      if (delta)
      {
        this.subscribeTo = newSubscriptionType;
  
        if (this.active)
          SUBSCRIPTION.changeSubscription(this, curSubscriptionType, newSubscriptionType);
  
        return true;
      }
  
      return false;
    }