final Strength valueStrength;
    final Equivalence<Object> keyEquivalence;
    final Equivalence<Object> valueEquivalence;
    final int concurrencyLevel;

    transient ConcurrentMap<K, V> delegate;

    AbstractSerializationProxy(
        Strength keyStrength,
        Strength valueStrength,
        Equivalence<Object> keyEquivalence,
        Equivalence<Object> valueEquivalence,

  @CanIgnoreReturnValue
  CacheBuilder<K, V> keyEquivalence(Equivalence<Object> equivalence) {
    checkState(keyEquivalence == null, "key equivalence was already set to %s", keyEquivalence);
    keyEquivalence = checkNotNull(equivalence);
    return this;
  }

  Equivalence<Object> getKeyEquivalence() {
    return MoreObjects.firstNonNull(keyEquivalence, getKeyStrength().defaultEquivalence());
  }

  /**