def parse(self, argv, command):
        """ Splits an argument list into an options dictionary and a fieldname
        list.

        The argument list, `argv`, must be of the form::

            *[option]... *[<field-name>]

        Options are validated and assigned to items in `command.options`. Field
        names are validated and stored in the list of `command.fieldnames`.

        #Arguments:

        :param command: Search command instance.
        :type command: ``SearchCommand``
        :param argv: List of search command arguments.
        :type argv: ``list``
        :return: ``None``

        #Exceptions:

        ``SyntaxError``: Argument list is incorrectly formed.
        ``ValueError``: Unrecognized option/field name, or an illegal field value.

        """
        # Prepare

        command_args = ' '.join(argv)
        command.fieldnames = None
        command.options.reset()

        command_args = SearchCommandParser._arguments_re.match(command_args)

        if command_args is None:
            raise SyntaxError("Syntax error: %s" % ' '.join(argv))

        # Parse options

        for option in SearchCommandParser._options_re.finditer(
                command_args.group('options')):
            name, value = option.group(1), option.group(2)
            if not name in command.options:
                raise ValueError((name, value) % 'Unrecognized option: %s = %s')
            command.options[name].value = SearchCommandParser.unquote(value)

        missing = command.options.get_missing()

        if missing is not None:
            if len(missing) == 1:
                raise ValueError('A value for "%s" is required' % missing[0])
            else:
                raise ValueError(
                    'Values for these options are required: %s' %
                    ', '.join(missing))

        # Parse field names

        command.fieldnames = command_args.group('fieldnames').split()
        command.logger.debug('%s: %s', type(command).__name__, command)
        return
dataset/ETHPy150Open hvandenb/splunk-elasticsearch/search-elasticsearch/bin/splunklib/searchcommands/search_command_internals.py/SearchCommandParser.parse/swapped operands of `%`