code: function (name) {
          var self = this, callback = self.settings[name], scope;
  
          if (!callback) {
            return;
          }
  
          // Look through lookup
          if (self.callbackLookup && (scope = self.callbackLookup[name])) {
            callback = scope.func;
            scope = scope.scope;
          }
  
          if (typeof callback === 'string') {
            scope = callback.replace(/\.\w+$/, '');
            scope = scope ? resolve(scope) : 0;
            callback = resolve(callback);
            self.callbackLookup = self.callbackLookup || {};
            self.callbackLookup[name] = { func: callback, scope: scope };
          }
  
          return callback.apply(scope || self, Array.prototype.slice.call(arguments, 1));
        }
docs: Executes a legacy callback. This method is useful to call old 2.x option callbacks.
  There new event model is a better way to add callback so this method might be removed in the future.
  
  @method execCallback
  @param {String} name Name of the callback to execute.
  @return {Object} Return value passed from callback function.