code: def get_buildkite_repo_branch() -> Tuple[str, str]:
      if "BUILDKITE_BRANCH" not in os.environ:
          return DEFAULT_REPO, DEFAULT_BRANCH
  
      branch_str = os.environ["BUILDKITE_BRANCH"]
  
      # BUILDKITE_PULL_REQUEST_REPO can be empty string, use `or` to catch this
      repo_url = os.environ.get(
          "BUILDKITE_PULL_REQUEST_REPO", None
      ) or os.environ.get("BUILDKITE_REPO", DEFAULT_REPO)
  
      if ":" in branch_str:
          # If the branch is user:branch, we split into user, branch
          owner, branch = branch_str.split(":", maxsplit=1)
  
          # If this is a PR, the repo_url is already set via env variable.
          # We only construct our own repo url if this is a branch build.
          if not os.environ.get("BUILDKITE_PULL_REQUEST_REPO"):
              repo_url = f"https://github.com/{owner}/ray.git"
      else:
          branch = branch_str
  
      repo_url = repo_url.replace("git://", "https://")
      return repo_url, branch
  
imports: import importlib
  import os
  import re
  import shlex
  import subprocess
  import sys
  from datetime import datetime
  import tempfile
  import time
  import urllib.request
  from typing import Optional, List, Tuple
  from ray_release.config import parse_python_version
  from ray_release.test import DEFAULT_PYTHON_VERSION
  from ray_release.template import set_test_env_var
  from ray_release.exception import RayWheelsUnspecifiedError, RayWheelsNotFoundError, RayWheelsTimeoutError, ReleaseTestSetupError
  from ray_release.logger import logger
  from ray_release.util import url_exists, python_version_str, resolve_url
  from ray_release.aws import upload_to_s3
label_desc: Use image node_id 9 for calling a global function with example usage: get_buildkite_repo_branch() and returns: repo_url,  branch, DEFAULT_REPO,  DEFAULT_BRANCH