code: function(model, collection, options) {
            options = options ? _.clone(options) : {};
            options.success =
              _.isFunction(options.success) ? options.success : function() {};
            var childRef = this.firebase.child(model.id);
            Backbone.Firebase._setWithCheck(childRef, null, _.bind(options.success, model));
          }
docs: Triggered when model.destroy() is called on one of the children.