class_docstr: Run source code which modifies a Document
  
      
docstr: If the handler fails, may contain a related error message.
  
          
docstr_tok: ["If","the","handler","fails",",","may","contain","a","related","error","message","."]
code: def error(self) -> str | None:
      """If the handler fails, may contain a related error message."""
      return self._runner.error
  
imports: from __future__ import annotations
  import logging
  from contextlib import contextmanager
  from os.path import basename, splitext
  from types import ModuleType
  from typing import Any, Callable, ClassVar
  from ...core.types import PathLike
  from ...document import Document
  from ...io.doc import curdoc, patch_curdoc
  from .code_runner import CodeRunner
  from .handler import Handler
label_desc: Use image node_id 2 for calling the CodeHandler obj's underlying member method code with example usage: obj.error() and returns: self