code: function(){
      this._regionManager = new Marionette.RegionManager();
  
      this.listenTo(this._regionManager, "region:add", function(name, region){
        this[name] = region;
      });
  
      this.listenTo(this._regionManager, "region:remove", function(name, region){
        delete this[name];
      });
    }
docs: Internal method to set up the region manager