code: def _standard_os_environ():
      """Set up ``os.environ`` at the start of the test session to have
      standard values. Returns a list of operations that is used by
      :func:`._reset_os_environ` after each test.
      """
      mp = monkeypatch.MonkeyPatch()
      out = (
          (os.environ, "FLASK_ENV_FILE", monkeypatch.notset),
          (os.environ, "FLASK_APP", monkeypatch.notset),
          (os.environ, "FLASK_DEBUG", monkeypatch.notset),
          (os.environ, "FLASK_RUN_FROM_CLI", monkeypatch.notset),
          (os.environ, "WERKZEUG_RUN_MAIN", monkeypatch.notset),
      )
  
      for _, key, value in out:
          if value is monkeypatch.notset:
              mp.delenv(key, False)
          else:
              mp.setenv(key, value)
  
      yield out
      mp.undo()
  
file_path: flask/tests/conftest.py
imports: import os
  import pkgutil
  import sys
  import pytest
  from _pytest import monkeypatch
  from flask import Flask
  from flask.globals import request_ctx
label_desc: Use image node_id 1 for calling a global function with example usage: _standard_os_environ() without return types