You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: page_at_rule.rs
    path of file: ./repos/lewp-rs/lewp-css/src/domain/at_rules/page
    
    the code of the file until where you have to start completion: // This file is part of css. It is subject to the license terms in 
    
    fn to_css<W: fmt::Write>(&self, dest: &mut W) -> fmt::Result {
        dest.write_str("@page")?;
        if let Some(ref page_selector_pseudo_class) =
            self.page_selector_pseudo_class
        {
            dest.write_char(' ')?;
            page_selector_pseudo_class.to_css(dest)?;
        }
        dest.write_char('{')?;
        self.property_declarations.to_css(dest)?;
        dest.write_char('}')
    }