docs: def modify_classes():
      """
      Auto-discover INSTALLED_APPS class_modifiers.py modules and fail silently when
      not present. This forces an import on them to modify any classes they
      may want.
      """
      import copy
      from django.conf import settings
      from django.contrib.admin.sites import site
      from django.utils.importlib import import_module
      from django.utils.module_loading import module_has_submodule
  
      for app in settings.INSTALLED_APPS:
          mod = import_module(app)
          # Attempt to import the app's class_modifier module.
          try:
              before_import_registry = copy.copy(site._registry)
              import_module('%s.class_modifiers' % app)
          except:
              site._registry = before_import_registry
              # Decide whether to bubble up this error. If the app just
              # doesn't have an class_modifier module, we can ignore the error
              # attempting to import it, otherwise we want it to bubble up.
              if module_has_submodule(mod, 'class_modifiers'):
                  raise