code: def _GetVSSStoreIdentifiers(self, scan_node):
      
      if not scan_node or not scan_node.path_spec:
        raise errors.ScannerError('Invalid scan node.')
  
      volume_system = vshadow_volume_system.VShadowVolumeSystem()
      volume_system.Open(scan_node.path_spec)
  
      volume_identifiers = self._source_scanner.GetVolumeIdentifiers(
          volume_system)
      if not volume_identifiers:
        return []
  
      if not self._mediator:
        raise errors.ScannerError(
            'Unable to proceed. VSS stores found but no mediator to determine '
            'how they should be used.')
  
      try:
        volume_identifiers = self._mediator.GetVSSStoreIdentifiers(
            volume_system, volume_identifiers)
  
      except KeyboardInterrupt:
        raise errors.UserAbort('File system scan aborted.')
  
      return self._NormalizedVolumeIdentifiers(
          volume_system, volume_identifiers, prefix='vss')
docs: Determines the VSS store identifiers.
  
      Args:
        scan_node (SourceScanNode): scan node.
  
      Returns:
        list[str]: VSS store identifiers.
  
      Raises:
        ScannerError: if the format the scan node is invalid or no mediator
            is provided and VSS store identifiers are found.
        UserAbort: if the user requested to abort.