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: mod.rs
    path of file: ./repos/Robyn/src/io_helpers
    
    the code of the file until where you have to start completion: use std::fs::File;
use std::io::Read;

use actix_web::HttpResponseBuilder;
use anyhow::Result;

use crate::types::headers::Headers;

// this should be something else
// probably inside the submodule
    
pub fn apply_hashmap_headers(response: &mut HttpResponseBuilder, headers: &Headers) {
    for iter in headers.headers.iter() {
        let (key, values) = iter.pair();
        for value in values {
            response.append_header((key.clone(), value.clone()));
        }
    }
}