code: def update_signing_cert(self, cert_id, status, user_name=None):
          
          params = {'CertificateId' : cert_id,
                    'Status' : status}
          if user_name:
              params['UserName'] = user_name
          return self.get_response('UpdateSigningCertificate', params)
docs: Change the status of the specified signing certificate from
          Active to Inactive or vice versa.
  
          If the user_name is not specified, it is determined implicitly based
          on the AWS Access Key ID used to sign the request.
  
          :type cert_id: string
          :param cert_id: The ID of the signing certificate
  
          :type status: string
          :param status: Either Active or Inactive.
  
          :type user_name: string
          :param user_name: The username of the user