code: public Operation addAccessConfig(
        String networkInterface, AccessConfig accessConfig, OperationOption... options) {
      return compute.addAccessConfig(getInstanceId(), networkInterface, accessConfig, options);
    }
docs: Adds an access configuration to the provided network interface for this instance.
  
  @return a zone operation if the add request was issued correctly, {@code null} if the instance
  was not found
  @throws ComputeException upon failure