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: main.rs
    path of file: ./repos/serenity/examples/e10_collectors/src
    
    the code of the file until where you have to start completion: //! This example will showcase the beauty of collectors. They allow to await messages or reactions
//! from a user in the middle of a control flow, one being a command.
#![allow(deprecated)] // We recommend migrating to poise, instead of using the standard command framework.
use std::collections::HashSet;
use std::env;
use std::time::Duration;

use serenity::async_trait;
use serenity::collector::MessageCollector;
use serenity::framework::standard::macros::{command, group, help};
use serenity::framework::standard::{
    help_commands,
    Args,
    CommandGroup,
    CommandResult,
    Configuration,
    HelpOptions,
    StandardFramework,
};
// Collectors are streams, that means we can use `StreamExt` and `TryStreamExt`.
use serenity::futures::stream::StreamExt;
use serenity::http::Http;
use serenity::model::prelude::*;
use serenity::prelude::*;

#[group("collector")]
#[commands(challenge)]
struct Collector;

#[help]
async fn my_help(
    context: &Context,
    msg: &Message,
    args: Args,
    help_optio
    
async fn main() {
    // Configure the client with your Discord bot token in the environment.
    let token = env::var("DISCORD_TOKEN").expect("Expected a token in the environment");

    let http = Http::new(&token);

    // We will fetch your bot's id.
    let bot_id = match http.get_current_user().await {
        Ok(info) => info.id,
        Err(why) => panic!("Could not access user info: {:?}", why),
    };

    let framework = StandardFramework::new().help(&MY_HELP).group(&COLLECTOR_GROUP);

    framework.configure(
        Configuration::new()
            .with_whitespace(true)
            .on_mention(Some(bot_id))
            .prefix("~")
            .delimiters(vec![", ", ","]),
    );

    let intents = GatewayIntents::GUILD_MESSAGES
        | GatewayIntents::DIRECT_MESSAGES
        | GatewayIntents::MESSAGE_CONTENT
        | GatewayIntents::GUILD_MESSAGE_REACTIONS;

    let mut client = Client::builder(&token, intents)
        .event_handler(Handler)
        .framework(framework)
        .await
        .expect("Err creating client");

    if let Err(why) = client.start().await {
        println!("Client error: {why:?}");
    }
}