code: def LVMPathSpecGetVolumeIndex(path_spec):
    
    volume_index = getattr(path_spec, 'volume_index', None)
  
    if volume_index is None:
      location = getattr(path_spec, 'location', None)
  
      if location is None or not location.startswith('/lvm'):
        return None
  
      volume_index = None
      try:
        volume_index = int(location[4:], 10) - 1
      except ValueError:
        pass
  
      if volume_index is None or volume_index < 0:
        return None
  
    return volume_index
docs: Retrieves the volume index from the path specification.
  
    Args:
      path_spec (PathSpec): path specification.
  
    Returns:
      int: volume index or None if not available.