docs: function(subscriptions){
        subscriptions = subscriptions || this.subscriptions;
        if (!subscriptions || _.isEmpty(subscriptions)) return;
        _.each(subscriptions, function(subscription, channel){
          if (_.isString(subscription)) {
            subscription = this[subscription];
          }
          Backbone.Mediator.unsubscribe(channel, subscription.$once || subscription, this);
        }, this);
      }