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/rspotify/src/clients
    
    the code of the file until where you have to start completion: mod base;
mod oauth;
pub mod pagination;

pub use base::BaseClient;
pub use oauth::OAuthClient;

use crate::ClientResult;

use std::fmt::Write as _;

use serde::Deserialize;

/// Converts a JSON response from Spotify into its model.
pub(crate) fn convert_result<'a, T: Deserialize<'a>>(input: &'a str) -> ClientResult<T> {
    serde_json::from_str::<T>(input).map_err(Into::into)
}

/// Append device ID to an API path.
pub(crate) fn 
    
    fn test_api_url() {
        let mut spotify = ClientCredsSpotify::default();
        assert_eq!(
            spotify.api_url("me/player/play"),
            "https://api.spotify.com/v1/me/player/play"
        );

        spotify.config = Config {
            api_base_url: String::from("http://localhost:8080/api/v1/"),
            ..Default::default()
        };
        assert_eq!(
            spotify.api_url("me/player/play"),
            "http://localhost:8080/api/v1/me/player/play"
        );

        // Also works without trailing character
        spotify.config = Config {
            api_base_url: String::from("http://localhost:8080/api/v1"),
            ..Default::default()
        };
        assert_eq!(
            spotify.api_url("me/player/play"),
            "http://localhost:8080/api/v1/me/player/play"
        );
    }