fn to_model(&self) -> anyhow::Result<Self::Model> {

        let mut calendar = crate::model::object::ICalObject::new();

        calendar.properties.reserve(self.properties.len());

        for property in &self.properties {

            calendar.properties.push(property.to_model()?);

        calendar.components.reserve(self.components.len());

        for component in &self.components {

            calendar.components.push(component.to_model()?);

        Ok(calendar)

    }