code: def __in_choice_context(self):
          
          for x in self.__stack:
              if x.__class__ is ChoiceFrame:
                  return True
          return False
docs: Whether we are currently processing a choice parameter group.
  
          This includes processing a parameter defined directly or indirectly
          within such a group.
  
          May only be called during parameter processing or the result will be
          calculated based on the context left behind by the previous parameter
          processing if any.