code: def invalid_fields(self, data, original_data):
          
          errors = []
  
          for field in original_data:
              # Skip nested fields because they will loop infinitely
              if isinstance(field, (set, list, tuple, dict)):
                  continue
  
              if field not in self.fields.keys():
                  errors.append(field)
  
          if errors:
              raise ValidationError("Invalid field", field_names=errors)
docs: Validator that checks if any keys provided aren't in the schema.
  
          Say your schema has support for keys ``a`` and ``b`` and the data
          provided has keys ``a``, ``b``, and ``c``. When the data is loaded into
          the schema, a :class:`marshmallow.ValidationError` will be raised
          informing the developer that excess keys have been provided.
  
          Raises:
              marshmallow.ValidationError: Raised if extra keys exist in the
                  passed in data.