ction must be used to set the property
       * @protected
       */
      _createPropertyAccessor(property, readOnly) {
        if (!this.hasOwnProperty('__dataHasAccessor')) {
          this.__dataHasAccessor = Object.assign({}, this.__dataHasAccessor);
        }
        if (!this.__dataHasAccessor[property]) {
          this.__dataHasAccessor[property] = true;
          saveAccessorValue(this, property);
          Object.defineProperty(this, property, {
            get: function() {
              return 