code: def _add_default_except_tags(except_tags: str) -> str:
      final_except_tags = set(DEFAULT_EXCEPT_TAGS)
      if except_tags:
          final_except_tags.update(except_tags.split(","))
      return ",".join(final_except_tags)
  
file_path: ray/ci/ray_ci/tester.py
imports: import os
  import sys
  from typing import List, Tuple, Optional
  import yaml
  import click
  from ci.ray_ci.container import _DOCKER_ECR_REPO
  from ci.ray_ci.builder_container import BuilderContainer, DEFAULT_BUILD_TYPE, DEFAULT_PYTHON_VERSION, DEFAULT_ARCHITECTURE, PYTHON_VERSIONS
  from ci.ray_ci.linux_tester_container import LinuxTesterContainer
  from ci.ray_ci.windows_tester_container import WindowsTesterContainer
  from ci.ray_ci.tester_container import TesterContainer
  from ci.ray_ci.utils import docker_login
  from ray_release.configs.global_config import init_global_config
  from ray_release.bazel import bazel_runfile
label_desc: Use image node_id 2 for calling a global function with example usage: _add_default_except_tags(except_tags) and returns: str