code: def _foo(arg=None):
      return "foo"
  
file_path: dvc/tests/unit/repo/experiments/queue/test_celery.py
imports: import time
  import pytest
  from celery import shared_task
  from celery.result import AsyncResult
  from dvc.exceptions import DvcException
  from dvc.repo.experiments.exceptions import UnresolvedExpNamesError
  from dvc.repo.experiments.queue.base import QueueDoneResult
  from dvc.repo.experiments.queue.exceptions import CannotKillTasksError
label_desc: Use image node_id 2 for calling a global function with example usage: _foo(arg) and returns: str