code: def _validate_schema(obj):
      
  
      if obj is not None and not isinstance(obj, Schema):
          raise IncompatibleSchema('Schema must be of type {0}'.format(Schema))
  
      return obj
docs: Ensures the passed schema instance is compatible
  
      :param obj: object to validate
      :return: obj
      :raises:
          - IncompatibleSchema if the passed schema is of an incompatible type