code: def update_thesis_supervisors(self):
          
          for field in record_get_field_instances(self.record, '701'):
              subs = list(field[0])
              subs.append(("e", "dir."))
              record_add_field(self.record, '700', subfields=subs)
          record_delete_fields(self.record, '701')
docs: 700 -> 701 Thesis supervisors.