code: def generate_user_agent(extra_ids = [])
        agent_app = @config.read('authentication.user_agent')
        if !agent_app.nil? && !agent_app.ascii_only?
          raise AdwordsApi::Errors::InvalidUserAgentError.new(
              'User agent contains non-ASCII characters.', agent_app)
        end
        extra_ids << ['AwApi-Ruby/%s' % AdwordsApi::ApiConfig::CLIENT_LIB_VERSION]
        super(extra_ids, agent_app)
      end
docs: Generates string to use as user agent in headers.