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: response.rb
    path of file: ./repos/global_sign/lib/global_sign/order_getter_by_order_id
    
    the code of the file until where you have to start completion: module GlobalSign
  module OrderGetterByOrderId
    class Response < GlobalSign::Response
      module XPath
        ORDER_ID            = '//Response/OrderID'
        ORDER_STATUS        = '//Response/OrderDetail/OrderInfo/OrderStatus'
        MODIFICATION_EVENTS = '//Response/OrderDetail/ModificationEvents'

        # options
        CERTIFICATE_INFO    = '//Response/OrderDetail/CertificateInfo'
        FULFILLMENT         = '//Response/OrderDetail/Fulfillment'
        CA_CERTIFICATES     = '//Response/OrderDetail/Fulfillment/CACertificates'
        SERVER_CERTIFICATE  = '//Response/OrderDetail/Fulfillment/ServerCertificate'
      end

      def response_header
        :OrderResponseHeader
      end

      def params
        return @p
    
      def params
        return @params if @params
        _params = {
          order_id:            @xml.xpath(XPath::ORDER_ID).text,
          order_status:        @xml.xpath(XPath::ORDER_STATUS).text,
          modification_events: modification_events_list
        }

        # options
        _params[:certificate_info] = {
          certificate_status: certificate_info.at('CertificateStatus').text,
          common_name:        certificate_info.at('CommonName').text,
          start_date:         certificate_info.at('StartDate').try(:text),
          end_date:           certificate_info.at('EndDate').try(:text),
          subject_name:       certificate_info.at('SubjectName').try(:text),
        } if certificate_info.text.present?

        _params[:fulfillment] = {
          ca_certificates: ca_certificates_list,
          server_certificate: {
            x509_cert:  server_certificate.at('X509Cert').text,
            pkcs7_cert: server_certificate.at('PKCS7Cert').text,
          }
        } if fulfillment.text.present?

        @params = _params
      end