class_docstr: Factory to create singleton instances of classes inheriting a given ``base`` class.
  
  .. seealso::
  
      :py:class:`orion.core.utils.GenericFactory`
code: def __init__(self, base: type[T]):
      super().__init__(base=base)
      self.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 GenericSingletonFactory object from inherited base classes: GenericFactory with example: obj = GenericSingletonFactory(base)