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: synhtml-css-classes.rs
    path of file: ./repos/syntect/examples
    
    the code of the file until where you have to start completion: //! Generates highlighted HTML with CSS classes for a Rust and a C++ source.
//! Run with ```cargo run --example synhtml-css-classes```
//!
//! will generate 4 files as usage example
//! * synhtml-css-classes.html
//! * synhtml-css-classes.css
//! * theme-dark.css
//! * theme-light.css
//!
//! You can open the html with a web browser and change between light and dark
//! mode.
use syntect::highlighting::ThemeSet;
use syntect::html::css_for_theme_with_class_style;
use syntect::html::{ClassedHTMLGenerator, ClassStyle};
use syntect::parsing::SyntaxSet;
use syntect::util::LinesWithEndings;


use std::fs::File;
use std::io::{BufWriter, Write};
use std::path::Path;

fn main() -> Result<(), std::io::Error> {
    // ---------------------------------------------------------------------------------------------
    // generate html
    let ss = SyntaxSet::load_defaults_newlines();

    let html_file =  File::create(Path::new("synhtml-css-classes.html"))?;
    let mut html = BufWriter::new(&html_file);

    // write html header
    writeln!(html, "<!DOCTYPE html>")?;
    writeln!(html, "<html>")?;
    writeln!(html, "  <head>")?;
    writeln!(html, "    <title>synhtml-css-classes.rs</title>")?;
    writeln!(html, "    <link rel=\"stylesheet\" href=\"synhtml-css-classes.css\">")?;
    writeln!(html, "  </head>")?;
    writeln!(html, "  <body>")?;

    // Rust
    let code_rs = "// Rust source
fn main() {
    println!(\"Hello World!\");
}";

    let sr_rs = ss.find_syntax_by_extension("rs").unwrap();
    let mut rs_html_generator = ClassedHTMLGenerator::new_with_class_style(sr_rs, &ss, ClassStyle::Spaced);
    for line in LinesWithEndings::from(code_rs) {
        rs_html_generator.parse_html_for_line_which_includes_newline(line).unwrap();
    }
    let html_rs = rs_html_generator.finalize();

    writeln!(html, "<pre class=\"code\">")?;
    writeln!
    
fn main() -> Result<(), std::io::Error> {
    // ---------------------------------------------------------------------------------------------
    // generate html
    let ss = SyntaxSet::load_defaults_newlines();

    let html_file =  File::create(Path::new("synhtml-css-classes.html"))?;
    let mut html = BufWriter::new(&html_file);

    // write html header
    writeln!(html, "<!DOCTYPE html>")?;
    writeln!(html, "<html>")?;
    writeln!(html, "  <head>")?;
    writeln!(html, "    <title>synhtml-css-classes.rs</title>")?;
    writeln!(html, "    <link rel=\"stylesheet\" href=\"synhtml-css-classes.css\">")?;
    writeln!(html, "  </head>")?;
    writeln!(html, "  <body>")?;

    // Rust
    let code_rs = "// Rust source
fn main() {
    println!(\"Hello World!\");
}";

    let sr_rs = ss.find_syntax_by_extension("rs").unwrap();
    let mut rs_html_generator = ClassedHTMLGenerator::new_with_class_style(sr_rs, &ss, ClassStyle::Spaced);
    for line in LinesWithEndings::from(code_rs) {
        rs_html_generator.parse_html_for_line_which_includes_newline(line).unwrap();
    }
    let html_rs = rs_html_generator.finalize();

    writeln!(html, "<pre class=\"code\">")?;
    writeln!(html, "{}", html_rs)?;
    writeln!(html, "</pre>")?;

    // C++
    let code_cpp = "/* C++ source */
#include <iostream>
int main() {
    std::cout << \"Hello World!\" << std::endl;
}";

    let sr_cpp = ss.find_syntax_by_extension("cpp").unwrap();
    let mut cpp_html_generator = ClassedHTMLGenerator::new_with_class_style(sr_cpp, &ss, ClassStyle::Spaced);
    for line in LinesWithEndings::from(code_cpp) {
        cpp_html_generator.parse_html_for_line_which_includes_newline(line).unwrap();
    }
    let html_cpp = cpp_html_generator.finalize();

    writeln!(html, "<pre class=\"code\">")?;
    writeln!(html, "{}", html_cpp)?;
    writeln!(html, "</pre>")?;

    // write html end
    writeln!(html, "  </body>")?;
    writeln!(html, "</html>")?;

    // ---------------------------------------------------------------------------------------------
    // generate css
    let css = "@import url(\"theme-light.css\") (prefers-color-scheme: light);
    @import url(\"theme-dark.css\") (prefers-color-scheme: dark);

    @media (prefers-color-scheme: dark) {
      body {
        background-color: gray;
      }
    }
    @media (prefers-color-scheme: light) {
      body {
        background-color: lightgray;
      }
    }";

    let css_file = File::create(Path::new("synhtml-css-classes.css"))?;
    let mut css_writer = BufWriter::new(&css_file);

    writeln!(css_writer, "{}", css)?;

    // ---------------------------------------------------------------------------------------------
    // generate css files for themes
    let ts = ThemeSet::load_defaults();

    // create dark color scheme css
    let dark_theme = &ts.themes["Solarized (dark)"];
    let css_dark_file = File::create(Path::new("theme-dark.css"))?;
    let mut css_dark_writer = BufWriter::new(&css_dark_file);

    let css_dark = css_for_theme_with_class_style(dark_theme, ClassStyle::Spaced).unwrap();
    writeln!(css_dark_writer, "{}", css_dark)?;

    // create light color scheme css
    let light_theme = &ts.themes["Solarized (light)"];
    let css_light_file = File::create(Path::new("theme-light.css"))?;
    let mut css_light_writer = BufWriter::new(&css_light_file);

    let css_light = css_for_theme_with_class_style(light_theme, ClassStyle::Spaced).unwrap();
    writeln!(css_light_writer, "{}", css_light)?;

    Ok(())
}