public abstract class C3 implements java.io.Serializable {  
  /**
   * A serialization method. 
   * @param s a serialization stream
   * @throws ClassNotFoundException if class not found
   * @throws java.io.IOException if an IO error
   * @serial
   */
  private void readObject​(java.io.ObjectInputStream s)
                 throws ClassNotFoundException,
                        java.io.IOException { }
}