code: public Operation attachDisk(
        PersistentDiskConfiguration configuration, OperationOption... options) {
      return compute.attachDisk(getInstanceId(), configuration, options);
    }
docs: Attaches a persistent disk to this instance given its configuration.
  
  @return a zone operation if the attach request was issued correctly, {@code null} if the
  instance was not found
  @throws ComputeException upon failure