code: def test_hadoop_is_file(tmpdir: str):
      a_file = f"{tmpdir}/test_hadoop_is_file.txt"
      with hadoop_open(a_file, "w") as f:
          f.write("HELLO WORLD")
  
      assert hl.hadoop_is_file(a_file)
      assert not hl.hadoop_is_file(f"{tmpdir}/")
      assert not hl.hadoop_is_file(f"{tmpdir}/invalid-path")
  
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 8 for calling a global function with example usage: test_hadoop_is_file(tmpdir) without return types