How to use the flake8.plugins.manager.Checkers function in flake8

"""Get a mock FileChecker class with plugin_target registered.

    Useful as a starting point for mocking reports/results.
    """
    # Mock an entry point returning the plugin target
    entry_point = mock.Mock(spec=['load'])
    entry_point.name = plugin_target.name
    entry_point.load.return_value = plugin_target

    # Load the checker plugins using the entry point mock
    with mock.patch.object(
            importlib_metadata,
            'entry_points',
            return_value={'flake8.extension': [entry_point]},
    ):
        checks = manager.Checkers()

    # Prevent it from reading lines from stdin or somewhere else
    with mock.patch('flake8.processor.FileProcessor.read_lines',
                    return_value=['Line 1']):
        file_checker = checker.FileChecker(
            '-',
            checks.to_dictionary(),
            mock.MagicMock()
        )
    return file_checker

:param config.ConfigFileFinder config_finder:
            The finder for finding and reading configuration files.
        :param str config_file:
            The optional configuraiton file to override all other configuration
            files (i.e., the --config option).
        :param bool ignore_config_files:
            Determine whether to parse configuration files or not. (i.e., the
            --isolated option).
        """
        local_plugins = config.get_local_plugins(
            config_finder, config_file, ignore_config_files
        )

        sys.path.extend(local_plugins.paths)

        self.check_plugins = plugin_manager.Checkers(local_plugins.extension)

        self.formatting_plugins = plugin_manager.ReportFormatters(
            local_plugins.report
        )

        self.check_plugins.load_plugins()
        self.formatting_plugins.load_plugins()

If :attr:`check_plugins`, :attr:`listening_plugins`, or
        :attr:`formatting_plugins` are ``None`` then this method will update
        them with the appropriate plugin manager instance. Given the expense
        of finding plugins (via :mod:`pkg_resources`) we want this to be
        idempotent and so only update those attributes if they are ``None``.
        """
        if self.local_plugins is None:
            self.local_plugins = config.get_local_plugins(
                self.config_finder,
                self.prelim_opts.config,
                self.prelim_opts.isolated,
            )

        if self.check_plugins is None:
            self.check_plugins = plugin_manager.Checkers(
                self.local_plugins.extension)

        if self.listening_plugins is None:
            self.listening_plugins = plugin_manager.Listeners()

        if self.formatting_plugins is None:
            self.formatting_plugins = plugin_manager.ReportFormatters(
                self.local_plugins.report)

        self.check_plugins.load_plugins()
        self.listening_plugins.load_plugins()
        self.formatting_plugins.load_plugins()