class_docstr: Tests the default Werkzeug implementation of TensorBoardServer.
  
  Mostly useful for IPv4/IPv6 testing. This test should run with only
  IPv4, only IPv6, and both IPv4 and IPv6 enabled.
code: def testSpecifiedHost(self):
      one_passed = False
      try:
          server = program.WerkzeugServer(
              self._StubApplication(),
              self.make_flags(host="127.0.0.1", port=0, path_prefix=""),
          )
          self.assertStartsWith(server.get_url(), "http://127.0.0.1:")
          one_passed = True
      except program.TensorBoardServerException:
          # IPv4 is not supported
          pass
      try:
          server = program.WerkzeugServer(
              self._StubApplication(),
              self.make_flags(host="::1", port=0, path_prefix=""),
          )
          self.assertStartsWith(server.get_url(), "http://[::1]:")
          one_passed = True
      except program.TensorBoardServerException:
          # IPv6 is not supported
          pass
      self.assertTrue(one_passed)
  
imports: import argparse
  import io
  import sys
  from unittest import mock
  from tensorboard import program
  from tensorboard import test
  from tensorboard.plugins import base_plugin
  from tensorboard.plugins.core import core_plugin
label_desc: Use image node_id 4 for calling the WerkzeugServerTest obj's underlying member method code with example usage: obj.testSpecifiedHost() without return types