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: string_custom_error_pattern.rs
    path of file: ./repos/failure/examples
    
    the code of the file until where you have to start completion: //! This exa
    
fn main() {
    let err = err1().unwrap_err();
    // Print the error itself
    println!("error: {}", err);
    // Print the chain of errors that caused it
    for cause in Fail::iter_causes(&err) {
        println!("caused by: {}", cause);
    }
}