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: pkey.rb
    path of file: ./repos/artichoke/artichoke-backend/vendor/ruby/ext/openssl/lib/openssl
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
#--
# Ruby/OpenSSL Project
# Copyright (C) 2017 Ruby/OpenSSL Project Authors
#++

require_relative 'marshal'

module OpenSSL::PKey
  class D
    
    def syssign(string)
      q or raise OpenSSL::PKey::DSAError, "incomplete DSA"
      private? or raise OpenSSL::PKey::DSAError, "Private DSA key needed!"
      begin
        sign_raw(nil, string)
      rescue OpenSSL::PKey::PKeyError
        raise OpenSSL::PKey::DSAError, $!.message
      end