code: def clear(cls):
      cls._instances = dict()
  
file_path: mars/mars/services/core.py
imports: import abc
  import asyncio
  import enum
  import importlib
  import inspect
  import warnings
  from typing import Dict, Iterable, List, Union
label_desc: Use image node_id 3 for calling the AbstractService obj's underlying member method code with example usage: obj.clear(cls) without return types