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: std.rs
    path of file: ./repos/gluon/format/tests
    
    the code of the file until where you have to start completion: extern crate gluon_base as base;
extern crate gluon_format as format;

use std::{
    env,
    fs::File,
    io::{Read, Write},
    path::{Path, PathBuf},
};

use difference::assert_diff;

use gluon::{RootedThread, ThreadExt, VmBuilder};

type Error = Box<dyn std::error::Error>;

fn new_vm() -> RootedThread {
    VmBuilder::new()
        .import_paths(Some(vec![".".into(), "..".into()]))
        .build()
}

fn test_format(name: &str) {
    let _ = env_logger::try_init();

    let mut contents = String::new();
    File::open(Path::ne
    
async fn main_() -> Result<(), Error> {
    let files = test_files("../std")?;

    let report = tensile::tokio_console_runner(
        tensile::group(
            "fmt",
            files
                .into_iter()
                .chain(Some(PathBuf::from("../repl/src/repl.glu")))
                .map(|file| {
                    let name = file.display().to_string();
                    tensile::test(name.clone(), move || test_format(&name))
                })
                .collect(),
        ),
        &Default::default(),
    )
    .await?;
    if !report.passes() {
        return Err("Some tests failed".into());
    }
    Ok(())
}