code: public <T> Completes<T> actorOf(final Class<T> protocol, final Address address) {
      return directoryScanner.actorOf(protocol, address).andThen(null, proxy -> proxy);
    }
docs: Answers the {@code Completes<T>} that will eventually complete with the {@code T} protocol
  of the backing {@code Actor} of the given {@code address}, or {@code null} if not found.
  @param <T> the protocol type
  @param protocol the {@code Class<T>} protocol supported by the backing {@code Actor}
  @param address the {@code Address} of the {@code Actor} to find
  @return {@code Completes<T>}