ixin) to
   * decide how/when to set these values back into the accessors.
   * If `model` is already an instance (it has a `__data` property), then
   * the value will be set as a pending property, meaning the user should
   * call `_invalidateProperties` or `_flushProperties` to take effect
   *
   * @param {Object} model Prototype or instance
   * @param {string} property Name of property
   * @private
   */
  function saveAccessorValue(model, property) {
    // Don't read/store value for any native prop