def _validate_schema(obj):
if obj is not None and not isinstance(obj, Schema):<EOL><INDENT>raise IncompatibleSchema('<STR_LIT>'.format(Schema))<EOL><DEDENT>return obj<EOL>
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