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: sys.rs
    path of file: ./repos/leetcode-cli/src/config
    
    the code of the file until where you have to start completion: //! System section
//!
//! This section is a set of constants after #88

use serde::{Deserialize, Serialize};

const CATEGORIES: [&str; 4] = ["algorithms", "concurrency", "database", "shell"];

// TODO: find a better solution.
fn categories() -> Vec<String> {
    CATEGORIES.into_iter().map(|s| s.into()).collect()
}

/// Leetcode API
#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct Urls {
    pub base: String,
    pub graphql: String,
    pub login: String,
    pub problems: String,
    pub problem: String,
    pub tag: String,
    pub test: String,
    pub session: String,
    pub submit: String,
    pub submissions: String,
    pub submission: String,
    pub verify: String,
    pub favorites: String,
    pub favorite_delete: String,
}

impl Default for Urls {
    fn default() -> Self {
  
    
    fn default() -> Self {
        Self {
            base: "https://leetcode.com".into(),
            graphql: "https://leetcode.com/graphql".into(),
            login: "https://leetcode.com/accounts/login/".into(),
            problems: "https://leetcode.com/api/problems/$category/".into(),
            problem: "https://leetcode.com/problems/$slug/description/".into(),
            tag: "https://leetcode.com/tag/$slug/".into(),
            test: "https://leetcode.com/problems/$slug/interpret_solution/".into(),
            session: "https://leetcode.com/session/".into(),
            submit: "https://leetcode.com/problems/$slug/submit/".into(),
            submissions: "https://leetcode.com/submissions/detail/$id/".into(),
            submission: "https://leetcode.com/submissions/detail/$id/".into(),
            verify: "https://leetcode.com/submissions/detail/$id/check/".into(),
            favorites: "https://leetcode.com/list/api/questions".into(),
            favorite_delete: "https://leetcode.com/list/api/questions/$hash/$id".into(),
        }
    }