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: setup.rb
    path of file: ./repos/bootcamp/lib/bootcamp
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Bootcamp
  class Setup
    class << self
      def fixtures_dir
        Rails.env.test? 
    
      def attach_book_cover!
        Book.order(:created_at).each_with_index do |book, i|
          filename = "#{i + 1}.jpg"
          path = Rails.root.join("#{fixtures_dir}/fixtures/files/books/covers/#{filename}")
          book.cover.attach(io: File.open(path), filename:) if File.exist?(path)
        end
      end