code: function (propertyName, newValue) {
              var oldValue = this.getProperty(propertyName);
              return oldValue === newValue || (oldValue == null && newValue == null);
          }
docs: Compare newValue with the one stored in _cfg[propertyName]. Can be overridden to have a specific comparison.
  Two values are considered equal if they are strictly equal, or if they are both either null or undefined (we
  consider them as being "void").
  @param {String} propertyName
  @param {MultiTypes} newValue If transformation is used, this should be the widget value and not the data
  model value
  @private
  @return {Boolean} true if values are considered as equal.