code: def add_choice(self, text, name='', identifier=None):
          
          if not utilities.is_string(text):
              raise InvalidArgument('text is not a string')
          choice_display_text = self._choice_text_metadata['default_string_values'][0]
          choice_display_text['text'] = text
          if identifier is None:
              identifier = str(ObjectId())
          choice = {
              'id': identifier,
              'text': text,
              'name': name
          }
          self.my_osid_object_form._my_map['choices'].append(choice)
          return choice
docs: stub