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: frontmatter.rs
    path of file: ./repos/cobalt.rs/src/cobalt_model
    
    the code of the file until where you have to start completion: use std::fmt;

use cobalt_config::DateTime;
use cobalt_config::SourceFormat;
use liquid;
use serde::Serialize;

use super::pagination;
use crate::error::Result;

#[derive(Debug, Eq, PartialEq, Default, Clone, Serialize)]
#[serde(deny_unknown_fields, default)]
pub struct Frontmatter {
    pub permalink: cobalt_config::Permalink,
    pub slug: liquid::model::KString,
    pub title: liquid::model
    
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let converted = serde_yaml::to_string(self).expect("should always be valid");
        let subset = converted
            .strip_prefix("---")
            .unwrap_or(converted.as_str())
            .trim();
        let converted = if subset == "{}" { "" } else { subset };
        if converted.is_empty() {
            Ok(())
        } else {
            write!(f, "{}", converted)
        }
    }