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": [{...}]})

def update_dbxref(self, feature_id, old_db, old_accession, new_db, new_accession, organism=None, sequence=None):
        """
        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": [{...}]})
        """
        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)