code: def testSubcommand(self):
      def define_flags(parser):
          parser.add_argument("--hello")
  
      tb = program.TensorBoard(
          plugins=[core_plugin.CorePluginLoader],
          assets_zip_provider=fake_asset_provider,
          subcommands=[_TestSubcommand(define_flags=define_flags)],
      )
      tb.configure(("tb", "test", "--hello", "world"))
      self.assertEqual(tb.main(), 0)
      _TestSubcommand.run.assert_called_once()
      flags = _TestSubcommand.run.call_args[0][0]
      self.assertEqual(flags.hello, "world")
  
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 5 for calling the SubcommandTest obj's underlying member method code with example usage: obj.testSubcommand() without return types