code: func diskRelocateString(relocate types.VirtualMachineRelocateSpecDiskLocator) string {
  	key := relocate.DiskId
  	var locstring string
  	if backing, ok := relocate.DiskBackingInfo.(*types.VirtualDiskFlatVer2BackingInfo); ok && backing != nil {
  		locstring = backing.FileName
  	} else {
  		locstring = relocate.Datastore.Value
  	}
  	return fmt.Sprintf("(%d => %s)", key, locstring)
  }
docs: // diskRelocateString prints out information from a
  // VirtualMachineRelocateSpecDiskLocator in a friendly way.
  //
  // The format depends on whether or not a backing has been defined.