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

        let playlist_name = parts

            .next()

            .ok_or(RequestParserError::UnexpectedEOF)?

            .to_string();

        let mode = parts

            .next()

            .map(|m| {

                m.parse()

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

            })

            .transpose()?;

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

        Ok((Request::Save(playlist_name, mode), ""))

    }

    fn parse_response(

        parts: ResponseAttributes<'_>,

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

        debug_assert!(parts.is_empty());

        Ok(())

    }