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: asset.rs
    path of file: ./repos/stellar-rust-sdk/cli/src/fmt/simple
    
    the code of the file until where you have to start completion: use super::Simple;
use fmt::Render;
use stellar_client::resources::{Asset, AssetIdentifier, Flags};

impl Render<Asset> for Simple 
    
    fn render(&self, flags: &Flags) -> Option<String> {
        let mut buf = String::new();
        if flags.is_auth_required() {
            append!(buf, "auth is required");
        }
        if flags.is_auth_revocable() {
            append!(buf, "auth is revocable");
        }
        Some(buf)
    }