code: function(containerView){
      if ("$itemViewContainer" in containerView){
        return containerView.$itemViewContainer;
      }
  
      var container;
      var itemViewContainer = Marionette.getOption(containerView, "itemViewContainer");
      if (itemViewContainer){
  
        var selector = _.isFunction(itemViewContainer) ? itemViewContainer() : itemViewContainer;
        container = containerView.$(selector);
        if (container.length <= 0) {
          throwError("The specified `itemViewContainer` was not found: " + containerView.itemViewContainer, "ItemViewContainerMissingError");
        }
  
      } else {
        container = containerView.$el;
      }
  
      containerView.$itemViewContainer = container;
      return container;
    }
docs: Internal method to ensure an `$itemViewContainer` exists, for the `appendHtml` method to use.