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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register_doi(self, submission_id, request_xml):
 """ 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. """


        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