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_metadata_service.rb
    path of file: ./repos/gitlabhq/app/services/packages/debian
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Packages
  module Debian
    class ExtractMetadataService
      include Gitlab::Utils::StrongMemoize

      ExtractionError = Class.new(StandardError)

      def initialize(package_file)
        @package_file = 
    
      def fields
        if file_type_debian?
          package_file.file.use_open_file(unlink_early: false) do |file|
            ::Packages::Debian::ExtractDebMetadataService.new(file.file_path).execute
          end
        elsif file_type_meta?
          package_file.file.use_open_file do |file|
            ::Packages::Debian::ParseDebian822Service.new(file.read).execute.each_value.first
          end
        end