* the proxy must be able to behave as the cache itself.
   */
  private static class ManualSerializationProxy<K, V> extends ForwardingCache<K, V>
      implements Serializable {
    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 1;

    final Strength keyStrength;
    final Strength valueStrength;

   * the proxy must be able to behave as the cache itself.
   */
  private static class ManualSerializationProxy<K, V> extends ForwardingCache<K, V>
      implements Serializable {
    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 1;

    final Strength keyStrength;
    final Strength valueStrength;