code: function(instance, methodName, handler, context) {
  				var prevSuper,
  					_super = instance[methodName] || $.noop;
  
  				instance[methodName] = function() {
  					var self = context || this;
  
  					try {
  						prevSuper = self._super;
  						self._super = _super;
  						return handler.apply(self, arguments);
  					} finally {
  						self._super = prevSuper;
  					}
  				};
  			}
docs: Return a wrapped handler method, that provides `this._super`.
  
  @example
  Implement `opts.createNode` event to add the 'draggable' attribute
  $.ui.fancytree.overrideMethod(ctx.options, "createNode", function(event, data) {
  Default processing if any
  this._super.apply(this, arguments);
  Add 'draggable' attribute
  data.node.span.draggable = true;
  });
  
  @param {object} instance
  @param {string} methodName
  @param {function} handler
  @param {object} [context] optional context