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: config.rs
    path of file: ./repos/cargo-mutants/tests
    
    the code of the file until where you have to start completion: // Copyright 2022, 2023 Martin Pool.

//! Test handling of `mutants.toml` configuration
    
fn write_config_file(tempdir: &TempDir, config: &str) {
    let path = tempdir.path();
    // This will error if it exists, which today it never will,
    // but perhaps later we should ignore that.
    create_dir(path.join(".cargo")).unwrap();
    write(path.join(".cargo/mutants.toml"), config.as_bytes()).unwrap();
}