code: def test_backend_context_manager():
      with LocalBackend() as backend:
          b = Batch(backend=backend)
          b.run()
  
imports: from typing import AsyncIterator
  import os
  import pytest
  import subprocess
  import tempfile
  from hailtop import pip_version
  from hailtop.batch import Batch, LocalBackend, ResourceGroup
  from hailtop.batch.resource import JobResourceFile
  from hailtop.batch.utils import concatenate
label_desc: Use image node_id 28 for calling a global function with example usage: test_backend_context_manager() without return types