code: def test_close(self):
      client = hdfs_test_client()
      assert client.is_open
      client.close()
      assert not client.is_open
  
      with pytest.raises(Exception):
          client.ls("/")
  
imports: import os
  import random
  from io import BytesIO
  from os.path import join
  import numpy
  import pytest
  import pyarrow
  from pyarrow.tests import util
  from pyarrow.tests.parquet.common import _test_dataframe
  from pyarrow.tests.parquet.test_dataset import _test_write_to_dataset_with_partitions, _test_write_to_dataset_no_partitions
  from pyarrow.util import guid
label_desc: Use image node_id 7 for calling the HdfsTestCases obj's underlying member method code with example usage: obj.test_close() without return types