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: languages.rs
    path of file: ./repos/rustacean/src/commands
    
    the code of the file until where you have to start completion: use crate::LangManager;

use serenity::{
    framework::standard::{macros::command, CommandResult},
    model::channel::Message,
    prelude::Context,
};

#[command]
#[aliases("langs", "language", "lang")]
#[description = "Get a list of available programming languages for the `exec` command."]
fn lang
    
fn languages(ctx: &mut Context, msg: &Message) -> CommandResult {
    let data = ctx.data.read();
    let lang_manager = data.get::<LangManager>().unwrap().lock().unwrap();
    let mut fields: Vec<(String, String, bool)> = Vec::new();
    for (lang_codes, boxed_lang) in lang_manager.get_languages() {
        if lang_manager.is_language_available(&(*boxed_lang)) {
            fields.push((
                boxed_lang.get_lang_name(),
                format!(
                    "({})",
                    lang_codes
                        .iter()
                        .map(|code| format!("`{}`", code))
                        .collect::<Vec<String>>()
                        .join(", ")
                ),
                true,
            ));
        }
    }
    fields.sort();

    let _ = msg.channel_id.send_message(&ctx, |m| {
        m.embed(|e| {
            e.title("Languages")
                .description("A list of available languages for the `exec` command.")
                .fields(fields)
        })
    })?;
    Ok(())
}