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/cross/src/docker
    
    the code of the file until where you have to start completion: mod build;
pub(crate) mod custom;
mod engine;
mod image;
mod local;
mod provided_images;
pub mod remote;
mod shared;

pub
    
pub fn image_name(target: &str, sub: Option<&str>, repository: &str, tag: &str) -> String {
    if let Some(sub) = sub {
        format!("{repository}/{target}:{tag}-{sub}")
    } else {
        format!("{repository}/{target}:{tag}")
    }
}