code: def update_keywords(self):
          
          for field in record_get_field_instances(self.record, '653', ind1='1'):
              subs = field_get_subfields(field)
              new_subs = []
              if 'a' in subs:
                  for val in subs['a']:
                      new_subs.extend([('9', 'author'), ('a', val)])
              new_field = create_field(subfields=new_subs, ind1='1')
              record_replace_field(
                  self.record, '653', new_field, field_position_global=field[4])
docs: 653 Free Keywords.