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: lib.rs
    path of file: ./repos/rerun/crates/re_smart_channel/src
    
    the code of the file until where you have to start completion: //! A channel that keeps track of latency and queue length.

use std::sync::{atomic::AtomicU64, Arc};

use web_time::Instant;

pub use crossbeam::channel::{RecvError, RecvTimeoutError, SendError, TryRecvError};

mod receive_set;
mod receiver;
mod sender;

pub use receive_set::ReceiveSet;
pub use receiver::Receiver;
pub use sender::Sender;

// --- Source ---

/// Identifies in what context this smart channel was creat
    
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&match self {
            SmartMessageSource::Unknown => "unknown".into(),
            SmartMessageSource::File(path) => format!("file://{}", path.to_string_lossy()),
            SmartMessageSource::RrdHttpStream { url } => format!("http://{url}"),
            SmartMessageSource::RrdWebEventCallback => "web_callback".into(),
            SmartMessageSource::Sdk => "sdk".into(),
            SmartMessageSource::WsClient { ws_server_url } => ws_server_url.clone(),
            SmartMessageSource::TcpClient { addr } => format!(
                "tcp://{}",
                addr.map_or_else(|| "(unknown ip)".to_owned(), |addr| addr.to_string())
            ),
            SmartMessageSource::Stdin => "stdin".into(),
        })
    }