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: source.rb
    path of file: ./repos/ruby-packer/ruby/lib/rubygems
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
autoload :FileUtils, 'fileutils'

require "rubygems/text"
##
# A Source knows how to list and fetch gems from a RubyGems marshal index.
#
# There are other Source subclasses for installed g
    
  def fetch_spec(name_tuple)
    fetcher = Gem::RemoteFetcher.fetcher

    spec_file_name = name_tuple.spec_name

    source_uri = uri + "#{Gem::MARSHAL_SPEC_DIR}#{spec_file_name}"

    cache_dir = cache_dir source_uri

    local_spec = File.join cache_dir, spec_file_name

    if File.exist? local_spec
      spec = Gem.read_binary local_spec
      spec = Marshal.load(spec) rescue nil
      return spec if spec
    end