*
   * @since 19.0
   */
  public static final class UnsupportedLoadingOperationException
      extends UnsupportedOperationException {
    // Package-private because this should only be thrown by loadAll() when it is not overridden.
    // Cache implementors may want to catch it but should not need to be able to throw it.
    UnsupportedLoadingOperationException() {}
  }

  /**