code: def register_doi(self, submission_id, request_xml):
          
  
          endpoint = self.get_endpoint('deposit')
  
          files = {
              'mdFile': ('%s.xml' % submission_id, request_xml)
          }
  
          params = {
              'operation': 'doMDUpload',
              'login_id': self.api_user,
              'login_passwd': self.api_key
          }
  
          result = self.do_http_request(
              'post',
              endpoint,
              data=params,
              files=files,
              timeout=10,
              custom_header=str(self.etiquette)
          )
  
          return result
docs: This method registry a new DOI number in Crossref or update some DOI
          metadata.
  
          submission_id: Will be used as the submission file name. The file name
          could be used in future requests to retrieve the submission status.
  
          request_xml: The XML with the document metadata. It must be under
          compliance with the Crossref Submission Schema.