code: def test_hadoop_exists(tmpdir: str):
      with hadoop_open(f"{tmpdir}/test_exists.txt", "w") as f:
          f.write("HELLO WORLD")
  
      r_exists = f"{tmpdir}/test_exists.txt"
      r_not_exists = f"{tmpdir}/not_exists.txt"
      assert hl.hadoop_exists(r_exists)
      assert not hl.hadoop_exists(r_not_exists)
  
imports: from typing import Generator
  import pytest
  import secrets
  import os
  import hail
  import hailtop.fs
  from hail.context import _get_local_tmpdir
  from hail.utils import hadoop_open, hadoop_copy, hadoop_ls
  from hailtop.utils import secret_alnum_string
  from hail.utils.java import FatalError
  from ..helpers import qobtest
label_desc: Use image node_id 7 for calling a global function with example usage: test_hadoop_exists(tmpdir) without return types