code: def populate_class_members(self, element_cls, prop_name):
          
          super(ZeroOrOneChoice, self).populate_class_members(
              element_cls, prop_name
          )
          self._add_choice_getter()
          for choice in self._choices:
              choice.populate_class_members(
                  element_cls, self._prop_name, self._successors
              )
          self._add_group_remover()
docs: Add the appropriate methods to *element_cls*.