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: gist.rs
    path of file: ./repos/gist/src
    
    the code of the file until where you have to start completion: use serde_json;

use crate::config::Config;
use crate::gist_file::GistFile;
use anyhow::Result;
use response::Response;
use std::collections::BTreeMap;
use std::env;
use ureq;

const GIST_API: &'static str = "https://api.github.com";
const GITHUB_TOKEN: &'static str = "GITHUB_TOKEN";
const GITHUB_GIST_TOKEN: &'static str = "GITHUB_GIST_TOKEN";
    
    pub fn list(&mut self, login: Option<String>) -> Result<Vec<Response>> {
        let url = self.gist_list_url(login);
        let resp = ureq::get(&url)
            .set("Authorization", &self.auth_header())
            .set("User-Agent", USER_AGENT)
            .set("Accept", ACCEPT_CONTENT)
            .set("Content-Type", CONTENT_TYPE)
            .query("per_page", "10")
            .call();

        match resp {
            Err(ureq::Error::Status(code, response)) => {
                Err(anyhow!("API error: ({}) {}", code, response.status_text()))
            }
            Err(e) => Err(anyhow!("error: {}", e.to_string())),
            Ok(response) => {
                let gl: Vec<Response> = response.into_json()?;
                Ok(gl)
            }
        }
    }