code: def check(self):
          
          super(NestedSetting, self).check()
          errors = []
          for subsetting in self.settings.values():
              try:
                  subsetting.check()
              except ValidationError as error:
                  errors.extend(error.messages)
          if errors:
              raise ValidationError(errors)
docs: Run the setting checker against the setting raw value.
  
          Raises:
              AttributeError: if the setting is missing and required.
              ValueError: (or other Exception) if the raw value is invalid.