pub fn new(subsystems: Option<Vec<SubSystem>>) -> Self {

        IdleRequest(subsystems)

    }

    fn serialize(&self) -> String {

        match &self.0 {

            Some(subsystems) => {

                let subsystems_str = subsystems

                    .iter()

                    .map(|subsystem| subsystem.to_string())

                    .collect::<Vec<_>>()

                    .join(",");

                format!("{} {}\n", Self::COMMAND, subsystems_str)

            None => Self::COMMAND.to_string() + "\n",

    }

    fn parse(parts: RequestTokenizer<'_>) -> Result<Self, RequestParserError> {

        let mut parts = parts;

        let result = parts.next().map_or(Ok(None), |subsystems| {

            let subsystems = subsystems

                .split(',')

                .map(|subsystem| SubSystem::from_str(subsystem).unwrap())

                .collect();

            Ok(Some(subsystems))

        });

        result.map(IdleRequest)

    }