fn parse_request(mut parts: std::str::SplitWhitespace<'_>) -> RequestParserResult<'_> {

        let playlist_name = parts

            .next()

            .ok_or(RequestParserError::UnexpectedEOF)?

            .to_string();

        let filter = parse_filter(&mut parts)?;

        let mut sort_or_window_or_position = parts.next();

        let mut sort = None;

        if let Some("sort") = sort_or_window_or_position {

            sort = Some(

                parts

                    .next()

                    .ok_or(RequestParserError::UnexpectedEOF)?

                    .to_string(),

            );

            sort_or_window_or_position = parts.next();

        }

        let mut window = None;

        if let Some("window") = sort_or_window_or_position {

            let w = parts.next().ok_or(RequestParserError::UnexpectedEOF)?;

                w.parse()

                    .map_err(|_| RequestParserError::SyntaxError(0, w.to_string()))?,

            sort_or_window_or_position = parts.next();

        }

        let mut position = None;

        if let Some("position") = sort_or_window_or_position {

            let p = parts.next().ok_or(RequestParserError::UnexpectedEOF)?;

                p.parse()

                    .map_err(|_| RequestParserError::SyntaxError(0, p.to_string()))?,

        }

        debug_assert!(parts.next().is_none());

        Ok((

            Request::SearchAddPl(playlist_name, filter, sort, window, position),

            "",

        ))

    }

    fn parse_response(

        parts: ResponseAttributes<'_>,

    ) -> Result<Self::Response, ResponseParserError> {

        unimplemented!()