code: def test_fallback_validator_with_iter_errors_using_ref(recwarn):
      """
      Test that when creating a standalone object (code_cell etc)
      the default validator is used as fallback.
      """
      set_validator("fastjsonschema")
      nbformat.v4.new_code_cell()
      nbformat.v4.new_markdown_cell()
      nbformat.v4.new_raw_cell()
      assert len(recwarn) == 0
  
imports: from __future__ import annotations
  import json
  import os
  import re
  from copy import deepcopy
  import pytest
  from jsonschema import ValidationError
  import nbformat
  from nbformat import read
  from nbformat.json_compat import VALIDATORS
  from nbformat.validator import isvalid, iter_validate, validate
  from nbformat.warnings import DuplicateCellId, MissingIDFieldWarning
  from .base import TestsBase
label_desc: Use image node_id 25 for calling a global function with example usage: test_fallback_validator_with_iter_errors_using_ref(recwarn) without return types