code: def is_pull_request():
      event_type = None
  
      for key in ["GITHUB_EVENT_NAME", "TRAVIS_EVENT_TYPE"]:
          event_type = os.getenv(key, event_type)
  
      if (
          os.environ.get("BUILDKITE")
          and os.environ.get("BUILDKITE_PULL_REQUEST", "false")
          != "false"
      ):
          event_type = "pull_request"
  
      return event_type == "pull_request"
  
file_path: ray/ci/pipeline/determine_tests_to_run.py
imports: from __future__ import absolute_import, division, print_function
  import argparse
  import json
  import os
  import re
  import subprocess
  import sys
  from pprint import pformat
  import traceback
label_desc: Use image node_id 2 for calling a global function with example usage: is_pull_request() and returns: unknown