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: extract_toc.rs
    path of file: ./repos/lopdf/examples
    
    the code of the file until where you have to start completion: use std::fmt::Debug;
use std::fs::File;
use std::io::{Error, ErrorKind, Write};
use std::path::{Path, PathBuf};
use std::time::Instant;

use clap::Parser;
use lopdf::{Document, Object};
use serde_json;
use shellexpand;

#[cfg(feature = "async")]
use tokio::runtime::Builder;

static IGNORE: &[&str] = &[
    "Length",
    "BBox",
    "FormType",
    "Matrix",
    "Resources",
    "Type",
    "XObject",
    "Subtype",
    "Filter",
    "ColorSpace",
    "Width",
    "Height",
    "BitsPerComponent",
    "Length1",
    "Length
    
fn main() -> Result<(), Error> {
    let args = Args::parse_args();

    let start_time = Instant::now();
    let pdf_path = PathBuf::from(shellexpand::full(args.pdf_path.to_str().unwrap()).unwrap().to_string());
    let output = match args.output {
        Some(o) => o.join(pdf_path.file_name().unwrap()),
        None => args.pdf_path,
    };
    let mut output = PathBuf::from(shellexpand::full(output.to_str().unwrap()).unwrap().to_string());
    output.set_extension("toc");
    pdf2toc(&pdf_path, &output, args.pretty)?;
    println!(
        "Done after {:.1} seconds.",
        Instant::now().duration_since(start_time).as_secs_f64()
    );
    Ok(())
}