code: public <T> T actorFor(final Class<T> protocol, final Definition definition, final Logger logger) {
      return actorFor(
              protocol,
              definition,
              definition.parentOr(world.defaultParent()),
              definition.supervisor(),
              logger);
    }
docs: Answers the {@code T} protocol of the newly created {@code Actor} that implements the {@code protocol} and
  that will be assigned the specific {@code logger}.
  @param <T> the protocol type
  @param protocol the {@code Class<T>} protocol
  @param definition the {@code Definition} used to initialize the newly created {@code Actor}
  @param logger the {@code Logger} to assign to the newly created {@code Actor}
  @return T