code: def test_error_decorator_custom() -> None:
      @v.error("E1")
      def good():
          return None
  
      assert good() == []
  
      @v.error("E2")
      def bad():
          return "bad"
  
      assert bad() == [
          ValidationIssue(
              9999, "EXT:E2", "Custom extension reports error", "bad"
          )
      ]
  
imports: from __future__ import annotations
  import pytest
  from typing import Any, cast
  from unittest.mock import MagicMock, patch
  from bokeh.core.properties import Int
  from bokeh.core.validation.check import ValidationIssue, ValidationIssues
  from bokeh.core.validation.issue import Error, Warning
  from bokeh.model import Model
  import bokeh.core.validation
label_desc: Use image node_id 3 for calling a global function with example usage: test_error_decorator_custom() and returns: None, str