code: def update_dbxref(self, feature_id, old_db, old_accession, new_db, new_accession, organism=None, sequence=None):
          
          data = {
              'features': [
                  {
                      'uniquename': feature_id,
                      'old_dbxrefs': [
                          {
                              'db': old_db,
                              'accession': old_accession,
                          }
                      ],
                      'new_dbxrefs': [
                          {
                              'db': new_db,
                              'accession': new_accession,
                          }
                      ]
                  }
              ]
          }
          data = self._update_data(data, organism, sequence)
          return self.post('deleteDbxref', data)
docs: Delete a dbxref from a feature
  
          :type feature_id: str
          :param feature_id: Feature UUID
  
          :type old_db: str
          :param old_db: Old DB Name (e.g. PMID)
  
          :type old_accession: str
          :param old_accession: Old accession Value
  
          :type new_db: str
          :param new_db: New DB Name (e.g. PMID)
  
          :type new_accession: str
          :param new_accession: New accession Value
  
          :type organism: str
          :param organism: Organism Common Name
  
          :type sequence: str
          :param sequence: Sequence Name
  
          :rtype: dict
          :return: A standard apollo feature dictionary ({"features": [{...}]})