code: def start_mongo():
      import pymongo
  
      subprocess.check_call(["service", "mongodb", "start"])
      mongo_url = "mongodb://localhost:27017"
      client = pymongo.MongoClient(mongo_url)
      # Make sure a clean slate for each test by dropping
      # previously created ones (if any).
      for db in client.list_database_names():
          # Keep the MongoDB default databases.
          if db not in ("admin", "local", "config"):
              client.drop_database(db)
      yield client, mongo_url
  
      subprocess.check_call(["service", "mongodb", "stop"])
  
file_path: ray/python/ray/data/tests/test_mongo.py
imports: import subprocess
  import pandas
  import pyarrow
  import pytest
  import ray
  from ray.data.tests.conftest import *
  from ray.data.tests.mock_http_server import *
  from ray.tests.conftest import *
label_desc: Use image node_id 1 for calling a global function with example usage: start_mongo() without return types