code: def __call__(cls, *args, **kwargs):
      """
      Possible changes to the value of the `__init__` argument do not affect
      the returned instance.
      """
      if cls not in cls._instances:
          instance = super().__call__(*args, **kwargs)
          cls._instances[cls] = instance
      else:
          assert (
              len(args) == 0 and len(kwargs) == 0
          ), f"{cls.__name__} is a singleton class and a instance has been created."
      return cls._instances[cls]
  
label_desc: Use image node_id 1 for calling the SingletonMeta obj's underlying member method code with example usage: obj.__call__(cls) and returns: cls