code: def __call__(cls, *args: Any, **kwargs: Any) -> Any:
      if cls not in cls._instances:
          cls._instances[cls] = super().__call__(*args, **kwargs)
      return cls._instances[cls]
  
file_path: hydra/hydra/core/singleton.py
imports: from copy import deepcopy
  from typing import Any, Dict
  from omegaconf.basecontainer import BaseContainer
label_desc: Use image node_id 1 for calling the Singleton obj's underlying member method code with example usage: obj.__call__(cls) and returns: cls