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: mixin.rb
    path of file: ./repos/second_level_cache/lib/second_level_cache
    
    the code of the file until where you have to start completion: # frozen_string_literal:
    
      def cache_version
        return @cache_version if defined? @cache_version
        # This line is copy from:
        # https://github.com/rails/rails/blob/f9a5f48/activerecord/lib/active_record/core.rb#L236
        attr_list = attribute_types.map { |name, type| "#{name}: #{type.type}" } * ", "
        model_schema_digest = Digest::MD5.hexdigest(attr_list)
        @cache_version = "#{second_level_cache_options[:version]}/#{model_schema_digest}"
      end