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: datetime.rs
    path of file: ./repos/config-rs/tests
    
    the code of the file until where you have to start completion: #![cfg(all(
    feature = "toml",
    feature = "json",
    feature = "yaml",
    feature = "ini",
    feature = "ron",
))]

use chrono::{DateTime, TimeZone, Utc};
use config::{Config, File, FileFormat};

fn make() -> Config {
    Config::builder()
        .add_source(File::from_str(
            r#"
            {
                "json_datetime": "201
    
fn test_datetime_string() {
    let s = make();

    // JSON
    let date: String = s.get("json_datetime").unwrap();

    assert_eq!(&date, "2017-05-10T02:14:53Z");

    // TOML
    let date: String = s.get("toml_datetime").unwrap();

    assert_eq!(&date, "2017-05-11T14:55:15Z");

    // YAML
    let date: String = s.get("yaml_datetime").unwrap();

    assert_eq!(&date, "2017-06-12T10:58:30Z");

    // INI
    let date: String = s.get("ini_datetime").unwrap();

    assert_eq!(&date, "2017-05-10T02:14:53Z");

    // RON
    let date: String = s.get("ron_datetime").unwrap();

    assert_eq!(&date, "2021-04-19T11:33:02Z");
}