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: header.rs
    path of file: ./repos/actix-web/actix-web/src/types
    
    the code of the file until where you have to start completion: //! For header extractor helper documentation, see [`Header`](crate::types::Header).

use std::{fmt, ops};

use actix_utils::future::{ready, Ready};

use crate::{
    dev::Payload, error::ParseError, extract::FromRequest, http::header::Header as ParseHeader,
    HttpRequest,
};

/// Extract typed headers from the request.
///
/// To extract a header, the inner type `T` must implement the
/// [`Header`](crate::http::header::Header) trait.
///
/// #
    
    async fn test_header_extract() {
        let (req, mut pl) = TestRequest::default()
            .insert_header((header::CONTENT_TYPE, mime::APPLICATION_JSON))
            .insert_header((header::ALLOW, header::Allow(vec![Method::GET])))
            .to_http_parts();

        let s = Header::<header::ContentType>::from_request(&req, &mut pl)
            .await
            .unwrap();
        assert_eq!(s.into_inner().0, mime::APPLICATION_JSON);

        let s = Header::<header::Allow>::from_request(&req, &mut pl)
            .await
            .unwrap();
        assert_eq!(s.into_inner().0, vec![Method::GET]);

        assert!(Header::<header::Date>::from_request(&req, &mut pl)
            .await
            .is_err());
    }