docs: def get_perm_model():
      """
      Returns the Perm model that is active in this project.
      """
      try:
          return django_apps.get_model(settings.PERM_MODEL, require_ready=False)
      except ValueError:
          raise ImproperlyConfigured("PERM_MODEL must be of the form 'app_label.model_name'")
      except LookupError:
          raise ImproperlyConfigured(
              "PERM_MODEL refers to model '{}' that has not been installed".format(settings.PERM_MODEL)
          )