code: def serialize_oaipmh(self, pid, record):
          
          root = etree.Element(
              'oai_datacite',
              nsmap={
                  None: 'http://schema.datacite.org/oai/oai-1.0/',
                  'xsi': 'http://www.w3.org/2001/XMLSchema-instance',
                  'xml': 'xml',
              },
              attrib={
                  '{http://www.w3.org/2001/XMLSchema-instance}schemaLocation':
                  'http://schema.datacite.org/oai/oai-1.0/ oai_datacite.xsd',
              }
          )
  
          root.append(E.isReferenceQuality(self.is_reference_quality))
          root.append(E.schemaVersion(self.serializer.version))
          root.append(E.datacentreSymbol(self.datacentre))
          root.append(E.payload(
              self.serializer.serialize_oaipmh(pid, record)
          ))
  
          return root
docs: Serialize a single record for OAI-PMH.