def check_unknown_fields(self, data, original_data):
        """Check for unknown keys."""
        if isinstance(original_data, list):
            for elem in original_data:
                self.check_unknown_fields(data, elem)
        else:
            for key in original_data:
                if key not in [
                        self.fields[field].attribute or field
                        for field in self.fields
                ]:
                    raise ValidationError(
                        'Unknown field name {}'.format(key), field_names=[key])