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/rusoto/service_crategen/src/commands/generate
    
    the code of the file until where you have to start completion: use std::collections::BTreeMap;
use std::fs::{self, OpenOptions};
use std::io::{BufWriter, Read, Write};
use std::path::Path;
use std::process::Command;

use rayon::prelude::*;
use toml;

mod codegen;

use crate::cargo;
use crate::{Service, ServiceConfig, ServiceDefinition};

fn generate_examples(crate_dir_path: &Path) -> Option<String> {
    let examples_dir_path = crate_dir_path.join("examples");

    if !examples_dir_path.exists() {
        return None;
    }

    let mut output = "//!\n//! # Examples\n".to_string();

    for dir_entry_result in fs::read_dir(&examples_dir_path).expect("failed to read examples dir") {
        let dir_entry = dir_entry_result.expect("failed to read examples dir");
        let mut contents = Vec::new();
        let mut file = fs
    
fn generate_examples(crate_dir_path: &Path) -> Option<String> {
    let examples_dir_path = crate_dir_path.join("examples");

    if !examples_dir_path.exists() {
        return None;
    }

    let mut output = "//!\n//! # Examples\n".to_string();

    for dir_entry_result in fs::read_dir(&examples_dir_path).expect("failed to read examples dir") {
        let dir_entry = dir_entry_result.expect("failed to read examples dir");
        let mut contents = Vec::new();
        let mut file = fs::File::open(dir_entry.path()).expect("failed to open example");
        file.read_to_end(&mut contents)
            .expect("failed to read from example file");
        let string_contents =
            String::from_utf8(contents).expect("example file has invalid encoding");

        output.push_str("//!\n");

        let mut inside_header_section = true;
        for line in string_contents.lines() {
            if line.starts_with("//!") {
                output.push_str(line);
                output.push('\n');
            } else {
                if inside_header_section {
                    // switching from header to code section
                    output.push_str("//!\n//! ```rust,no_run\n");
                    inside_header_section = false;
                }
                output.push_str("//! ");
                output.push_str(line);
                output.push('\n');
            }
        }
        output.push_str("//! ```\n");
    }

    Some(output)
}