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: lib.rs
    path of file: ./repos/Theseus/applications/lspci/src
    
    the code of the file until where you have to start completion: //! This application lists currently connected PCI devices.

#![no_std]

extern crate alloc;
#[macro_use] extern crate app_io;
extern crate getopts;

use alloc::vec::Vec;
use alloc::string::String;
use getopts::Options;
use pci::pci_device_iter;
use memory::PhysicalAddress;

pub fn main(args: Vec<String>) -> isize {
    let mut opts = Options::new();
    opts.optflag("h", "help", "print this help menu");

    let matches = match opts.parse(args) {
    
pub fn main(args: Vec<String>) -> isize {
    let mut opts = Options::new();
    opts.optflag("h", "help", "print this help menu");

    let matches = match opts.parse(args) {
        Ok(m) => m,
        Err(_f) => {
            println!("{}", _f);
            print_usage(opts);
            return -1; 
        }
    };

    if matches.opt_present("h") {
        print_usage(opts);
        return 0;
    }

    if let Err(msg) = list_pci_devices() {
        println!("Error: {}", msg);
    }

    0
}