code: def _assert_output(self, fn, regex_str):
      stdout = io.StringIO()
      with contextlib.redirect_stdout(stdout):
          fn()
      output = stdout.getvalue()
      self.assertRegex(output, re.compile(regex_str, re.DOTALL))
  
imports: import contextlib
  import io
  import os
  import re
  import keras_tuner
  import tensorflow
  from tensorflow import keras
  from tensorflow_cloud.tuner import vizier_client
  from tensorflow_cloud.tuner.tuner import DistributingCloudTuner
label_desc: Use image node_id 2 for calling the _DistributingCloudTunerIntegrationTestBase obj's underlying member method code with example usage: obj._assert_output(fn, regex_str) without return types