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/cargo-download/src
    
    the code of the file until where you have to start completion: //!
//! cargo-download
//!

             extern crate ansi_term;
#[macro_use] extern crate clap;
             extern crate conv;
#[macro_use] extern crate derive_error;
             extern crate exitcode;
             extern cra
    
fn print_args_error(e: ArgsError) -> io::Result<()> {
    match e {
        ArgsError::Parse(ref e) =>
            // In case of generic parse error,
            // message provided by the clap library will be the usage string.
            writeln!(&mut io::stderr(), "{}", e.message),
        e => {
            writeln!(&mut io::stderr(), "Failed to parse arguments: {}", e)
        }
    }
}