with OkHttp 3.x: must use `object :` with OkHttp 4.x:

Kotlin calling OkHttp 3.x:

```kotlin
val client = OkHttpClient.Builder()
    .dns { hostname -> InetAddress.getAllByName(hostname).toList() }
    .build()
```

Kotlin calling OkHttp 4.x:

```kotlin
val client = OkHttpClient.Builder()
    .dns(object : Dns {

) : Dns {
  @Throws(UnknownHostException::class)
  override fun lookup(hostname: String): List<InetAddress> {
    if (this.dnsHostname != hostname) {
      throw UnknownHostException(
        "BootstrapDns called for $hostname instead of $dnsHostname",
      )
    }

    return dnsServers
  }

   * fact the static type of {@link Throwable} is occasionally justified even for a method with no
   * {@code throws} clause: Some such methods can in fact throw a checked exception (e.g., by
   * calling code written in Kotlin).) Typically, we want to let a {@link Throwable} from such a
   * method propagate untouched, just as we'd typically let it do for a non-reflective call.

An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

This provider might be charging you per request, and calling it might take some extra time than if you had a fixed mock user for tests.

You probably want to test the external provider once, but not necessarily call it for every test that runs.

   * this graph.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}
   * {@code view} returned by this method will be invalidated, and will throw {@code
   * IllegalStateException} if it is accessed in any way, with the following exceptions:
   *
   * <ul>

     */
    @Override
    public boolean equals(final Object obj) {
        return obj instanceof UniAddress && this.addr.equals(((UniAddress) obj).addr);
    }

    /**
     * Guess first called name to try for session establishment. This
     * method is used exclusively by the <code>jcifs.smb</code> package.
     *
     * @return the guessed name
     */
    @Override
    public String firstCalledName() {

     */
    public interface WitnessNotificationListener {
        /**
         * Called when a witness notification is received.
         *
         * @param notification the witness notification
         */
        void onWitnessNotification(WitnessNotification notification);

        /**
         * Called when a witness registration fails.
         *
         * @param registration the failed registration

   * fact the static type of {@link Throwable} is occasionally justified even for a method with no
   * {@code throws} clause: Some such methods can in fact throw a checked exception (e.g., by
   * calling code written in Kotlin).) Typically, we want to let a {@link Throwable} from such a
   * method propagate untouched, just as we'd typically let it do for a non-reflective call.

   * fact the static type of {@link Throwable} is occasionally justified even for a method with no
   * {@code throws} clause: Some such methods can in fact throw a checked exception (e.g., by
   * calling code written in Kotlin).) Typically, we want to let a {@link Throwable} from such a
   * method propagate untouched, just as we'd typically let it do for a non-reflective call.

        assertTrue("Then callback should complete", latch.await(10, TimeUnit.SECONDS));
        Thread.sleep(100); // Wait a bit to ensure error callback isn't called
        assertEquals("Then callback should be invoked", 1, thenCount.get());
        assertEquals("Error callback should not be invoked", 0, errorCount.get());
    }

    @Test