code: def check_unknown_fields(self, data, original_data):
          
          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])
docs: Check for unknown keys.