docs: def listSnapshotDir(kls, path):
  		"""Return the set of snapshot directories and non-snapshot directories
  		under the given path."""
  		snapshotSet    = set()
  		nonsnapshotSet = set()
  		try:
  			entryList = os.listdir(path)
  			for e in entryList:
  				if kls.isFilenameInteger(e): snapshotSet   .add(e)
  				else:                        nonsnapshotSet.add(e)
  		except FileNotFoundError: pass
  		finally:
  			return snapshotSet, nonsnapshotSet