code: public <K2 extends K, V2 extends V> ExpiryPolicyBuilder<K2, V2> update(TriFunction<K2, Supplier<? extends V2>, V2, Duration> update) {
      return new ExpiryPolicyBuilder<>(create, access, Objects.requireNonNull(update));
    }
docs: Set a function giving the TTL since last update.
  <p>
  Note: Calling this method on a builder with an existing TTL since last update will override the previous value or function.
  
  @param update Function giving the TTL since last update
  @return a new builder with the TTL since last update calculation function