class_docstr: A base class for Bokeh properties with simple get/set and serialization
  behavior.
class_docstr_tok: ["A","base","class","for","Bokeh","properties","with","simple","get\/set","and","serialization","behavior","."]
code: def is_unstable(cls, value: Any) -> TypeGuard[Callable[[], Any]]:
      from .instance import InstanceDefault
  
      return isinstance(value, (FunctionType, InstanceDefault))
  
imports: from __future__ import annotations
  import logging
  from copy import copy
  from types import FunctionType
  from typing import TYPE_CHECKING, Any, Callable, Generic, TypeVar
  from ...util.deprecation import deprecated
  from .singletons import Undefined
  from .wrappers import PropertyValueColumnData, PropertyValueContainer
label_desc: Use image node_id 15 for calling the PropertyDescriptor obj's underlying member method code with example usage: obj.is_unstable(cls, value) and returns: isinstance