class_docstr: Metaclass that implements the singleton pattern for a Python class.
docstr: Create a class instance variable and initiate it to None object.
docstr_tok: ["Create","a","class","instance","variable","and","initiate","it","to","None","object","."]
code: def __init__(cls, name, bases, dictionary):
      """Create a class instance variable and initiate it to None object."""
      super().__init__(name, bases, dictionary)
      cls.instance = None
  
imports: from __future__ import annotations
  from abc import ABCMeta
  from orion.core.utils import Factory, GenericFactory, T
label_desc: Use image node_id 1 to create a new SingletonType object from inherited base classes: type with example: obj = SingletonType(cls, name, bases, dictionary)