fn write_model<W: Write>(&self, writer: &mut W) -> anyhow::Result<()> {

        writer.write_all(b"BEGIN:VCALENDAR")?;

        for property in &self.properties {

            writer.write_all(b"\r\n")?;

            property.write_model(writer)?;

        for component in &self.components {

            writer.write_all(b"\r\n")?;

            component.write_model(writer)?;

        writer.write_all(b"\r\nEND:VCALENDAR\r\n")?;

        Ok(())

    }

    fn write_model<W: Write>(&self, writer: &mut W) -> anyhow::Result<()> {

        use crate::model::property::CalendarProperty;

        match self {

            CalendarProperty::ProductId(property) => {

                writer.write_all(b"PRODID")?;

                property.params.as_slice().write_model(writer)?;

                writer.write_all(b":")?;

                writer.write_all(property.value.as_bytes())?;

            CalendarProperty::Version(property) => {

                writer.write_all(b"VERSION")?;

                property.params.as_slice().write_model(writer)?;

                writer.write_all(b":")?;

                if let Some(min_version) = &property.min_version {

                }

                writer.write_all(property.max_version.as_bytes())?;

            CalendarProperty::CalendarScale(property) => {

                writer.write_all(b"CALSCALE")?;

                property.params.as_slice().write_model(writer)?;

                writer.write_all(b":")?;

                writer.write_all(property.value.as_bytes())?;

            CalendarProperty::Method(property) => {

                writer.write_all(b"METHOD")?;

                property.params.as_slice().write_model(writer)?;

                writer.write_all(b":")?;

                writer.write_all(property.value.as_bytes())?;

        Ok(())

    }