def parse_known_args(self, args = None, namespace = None,
                         config_file_contents = None, env_vars = os.environ):
        """Supports all the same args as the ArgumentParser.parse_args(..),
        as well as the following additional args.

        Additional Args:
            args: a list of args as in argparse, or a string (eg. "-x -y bla")
            config_file_contents: String. Used for testing.
            env_vars: Dictionary. Used for testing.
        """
        if args is None:
            args = sys.argv[1:]
        elif type(args) == str:
            args = args.split()
        else:
            args = list(args)

        # normalize args by converting args like --key=value to --key value
        normalized_args = list()
        for arg in args:
            if arg and arg[0] in self.prefix_chars and '=' in arg:
                key, value =  arg.split('=', 1)
                normalized_args.append(key)
                normalized_args.append(value)
            else:
                normalized_args.append(arg)
        args = normalized_args

        for a in self._actions:
            a.is_positional_arg = not a.option_strings

        # maps a string describing the source (eg. env var) to a settings dict
        # to keep track of where values came from (used by print_values()).
        # The settings dicts for env vars and config files will then map
        # the config key to an (argparse Action obj, string value) 2-tuple.
        self._source_to_settings = OrderedDict()
        if args:
            a_v_pair = (None, list(args))  # copy args list to isolate changes
            self._source_to_settings[_COMMAND_LINE_SOURCE_KEY] = {'': a_v_pair}

        # handle auto_env_var_prefix __init__ arg by setting a.env_var as needed
        if self._auto_env_var_prefix is not None:
            for a in self._actions:
                config_file_keys = self.get_possible_config_keys(a)
                if config_file_keys and not (a.env_var or a.is_positional_arg
                    or a.is_config_file_arg or a.is_write_out_config_file_arg or
                    type(a) == argparse._HelpAction):
                    stripped_config_file_key = config_file_keys[0].strip(
                        self.prefix_chars)
                    a.env_var = (self._auto_env_var_prefix +
                                 stripped_config_file_key).replace('-', '_').upper()

        # add env var settings to the commandline that aren't there already
        env_var_args = []
        actions_with_env_var_values = [a for a in self._actions
            if not a.is_positional_arg and a.env_var and a.env_var in env_vars
                and not already_on_command_line(args, a.option_strings)]
        for action in actions_with_env_var_values:
            key = action.env_var
            value = env_vars[key]  # TODO parse env var values here to allow lists?
            env_var_args += self.convert_item_to_command_line_arg(
                action, key, value)

        args = env_var_args + args

        if env_var_args:
            self._source_to_settings[_ENV_VAR_SOURCE_KEY] = OrderedDict(
                [(a.env_var, (a, env_vars[a.env_var]))
                    for a in actions_with_env_var_values])


        # before parsing any config files, check if -h was specified.
        supports_help_arg = any(
            a for a in self._actions if type(a) == argparse._HelpAction)
        skip_config_file_parsing = supports_help_arg and (
            "-h" in args or "--help" in args)

        # prepare for reading config file(s)
        known_config_keys = dict((config_key, action) for action in self._actions
            for config_key in self.get_possible_config_keys(action))

        # open the config file(s)
        config_streams = []
        if config_file_contents:
            stream = StringIO(config_file_contents)
            stream.name = "method arg"
            config_streams = [stream]
        elif not skip_config_file_parsing:
            config_streams = self._open_config_files(args)

        # parse each config file
        for stream in reversed(config_streams):
            try:
                config_items = self._config_file_parser.parse(stream)
            except ConfigFileParserException as e:
                self.error(e)
            finally:
                if hasattr(stream, "close"):
                    stream.close()

            # add each config item to the commandline unless it's there already
            config_args = []
            for key, value in config_items.items():
                if key in known_config_keys:
                    action = known_config_keys[key]
                    discard_this_key = already_on_command_line(
                        args, action.option_strings)
                else:
                    action = None
                    discard_this_key = self._ignore_unknown_config_file_keys or \
                        already_on_command_line(
                            args,
                            self.get_command_line_key_for_unknown_config_file_setting(key))

                if not discard_this_key:
                    config_args += self.convert_item_to_command_line_arg(
                        action, key, value)
                    source_key = "%s|%s" %(_CONFIG_FILE_SOURCE_KEY, stream.name)
                    if source_key not in self._source_to_settings:
                        self._source_to_settings[source_key] = OrderedDict()
                    self._source_to_settings[source_key][key] = (action, value)

            args = config_args + args


        # save default settings for use by print_values()
        default_settings = OrderedDict()
        for action in self._actions:
            cares_about_default_value = (not action.is_positional_arg or
                action.nargs in [OPTIONAL, ZERO_OR_MORE])
            if (already_on_command_line(args, action.option_strings) or
                    not cares_about_default_value or
                    action.default is None or
                    action.default == SUPPRESS or
                    type(action) in ACTION_TYPES_THAT_DONT_NEED_A_VALUE):
                continue
            else:
                if action.option_strings:
                    key = action.option_strings[-1]
                else:
                    key = action.dest
                default_settings[key] = (action, str(action.default))

        if default_settings:
            self._source_to_settings[_DEFAULTS_SOURCE_KEY] = default_settings

        # parse all args (including commandline, config file, and env var)
        namespace, unknown_args = argparse.ArgumentParser.parse_known_args(
            self, args=args, namespace=namespace)

        # handle any args that have is_write_out_config_file_arg set to true
        user_write_out_config_file_arg_actions = [a for a in self._actions
            if getattr(a, "is_write_out_config_file_arg", False)]
        if user_write_out_config_file_arg_actions:
            output_file_paths = []
            for action in user_write_out_config_file_arg_actions:
                # check if the user specified this arg on the commandline
                output_file_path = getattr(namespace, action.dest, None)
                if output_file_path:
                    # validate the output file path
                    try:
                        with open(output_file_path, "w") as output_file:
                            output_file_paths.append(output_file_path)
                    except __HOLE__ as e:
                        raise ValueError("Couldn't open %s for writing: %s" % (
                            output_file_path, e))

            if output_file_paths:
                # generate the config file contents
                config_items = self.get_items_for_config_file_output(
                    self._source_to_settings, namespace)
                file_contents = self._config_file_parser.serialize(config_items)
                for output_file_path in output_file_paths:
                    with open(output_file_path, "w") as output_file:
                        output_file.write(file_contents)
                if len(output_file_paths) == 1:
                    output_file_paths = output_file_paths[0]
                self.exit(0, "Wrote config file to " + str(output_file_paths))
        return namespace, unknown_args
dataset/ETHPy150Open bw2/ConfigArgParse/configargparse.py/ArgumentParser.parse_known_args