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/risc0/bonsai/ethereum-relay/src
    
    the code of the file until where you have to start completion: // Copyright 2024 RISC Zero, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the 
    
async fn maybe_start_local_bonsai(dev_mode: bool, bonsai_url: String) -> anyhow::Result<()> {
    if dev_mode {
        let bonsai_url = Url::parse(&bonsai_url)?;
        let port = bonsai_url.port_or_known_default().unwrap();
        let listener = TcpListener::bind(format!("0.0.0.0:{port}")).await?;
        return bonsai_rest_api_mock::serve(listener).await;
    }

    Ok(())
}