code: public <T> T actorAs(final Actor actor, final Class<T> protocol) {
      return actorProxyFor(protocol, actor, actor.lifeCycle.environment.mailbox);
    }
docs: Answers the {@code T} protocol type as the means to message the backing {@code Actor}.
  @param actor the {@code Actor} that implements the {@code Class<T>} protocol
  @param protocol the {@code Class<T>} protocol
  @param <T> the protocol type
  @return T