class_docstr: Abstract base class for a file lock object.
docstr: :return: a flag indicating if this lock is singleton or not
code: def is_singleton(self) -> bool:
      """:return: a flag indicating if this lock is singleton or not"""
      return self._is_singleton
  
imports: from __future__ import annotations
  import contextlib
  import logging
  import os
  import time
  import warnings
  from abc import ABC, abstractmethod
  from dataclasses import dataclass
  from threading import local
  from typing import TYPE_CHECKING, Any, ClassVar
  from weakref import WeakValueDictionary
  from ._error import Timeout
label_desc: Use image node_id 4 for calling the BaseFileLock obj's underlying member method code with example usage: obj.is_singleton() and returns: self