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: response.rs
    path of file: ./repos/lettre/src/transport/smtp
    
    the code of the file until where you have to start completion: //! SMTP response, containing a mandatory return code and an optional text
//! message

use std::{
    fmt::{Display, Formatter, Result},
    result,
    str::Fro
    
    fn test_code_new() {
        assert_eq!(
            Code::new(
                Severity::TransientNegativeCompletion,
                Category::Connections,
                Detail::Zero,
            ),
            Code {
                severity: Severity::TransientNegativeCompletion,
                category: Category::Connections,
                detail: Detail::Zero,
            }
        );
    }