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: listing11.rs
    path of file: ./repos/mun/book/listings/ch04-structs
    
    the code of the file until where you have to start completion: # extern crate mun_runtime;
use mun_runtime::{Runtime, StructRef};
use std::env;

fn main() {
    let lib_path = env::args().nth(1).expect("Expected path to a Mun library.");

    // Safety: We assume that the libra
    
fn main() {
    let lib_path = env::args().nth(1).expect("Expected path to a Mun library.");

    // Safety: We assume that the library that is loaded is a valid munlib
    let builder = Runtime::builder(lib_path);
    let mut runtime = unsafe { builder.finish() }
        .expect("Failed to spawn Runtime");

    let a: StructRef = runtime.invoke("vector2_new", (-1.0f32, 1.0f32)).unwrap();
    let b: StructRef = runtime.invoke("vector2_new", (1.0f32, -1.0f32)).unwrap();
    let added: StructRef = runtime.invoke("vector2_add", (a, b)).unwrap();
}