{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "allOf": [
        {
            "$ref": "#/definitions/Pets"
        }
    ],
    "definitions": {
        "Pets": {
            "type": "string",
            "enum": [
                "cat",
                "dog",
                "parrot",
                "hamster"
            ]
        }
    }
}