code: def valid_value(self, value):
          
          if isinstance(value, Constant):
              value = value.name
          text_value = force_text(value)
          for option_value, option_label, option_title in self.choices:
              if value == option_value or text_value == force_text(option_value):
                  return True
          return False
docs: Check if the provided value is a valid choice.