// value automatically if one of them is empty and the other is non-empty.
  // When namespace is specified in dataSourceRef,
  // dataSource isn't set to the same value and must be empty.
  // There are three important differences between dataSource and dataSourceRef:
  // * While dataSource only allows two specific types of objects, dataSourceRef
  //   allows any non-core object, as well as PersistentVolumeClaim objects.