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

        let filter = parse_filter(&mut parts)?;

        let mut sort_or_window = parts.next();

        let mut sort = None;

        if let Some("sort") = sort_or_window {

            sort = Some(

                parts

                    .next()

                    .ok_or(RequestParserError::UnexpectedEOF)?

                    .to_string(),

            );

            sort_or_window = parts.next();

        }

        let mut window = None;

        if let Some("window") = sort_or_window {

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

                w.parse()

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

        }

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

        Ok((Request::PlaylistSearch(filter, sort, window), ""))

    }

    fn parse_response(

        _parts: ResponseAttributes<'_>,

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

        unimplemented!()