def METHOD_NAME(petstore_spec):
    Pet = petstore_spec.definitions['Pet']
    pet_id = 1
    pet_name = 'Darwin'
    pet_photo_urls = []
    pet = Pet(id=pet_id, name=pet_name, photoUrls=pet_photo_urls)
    marshalled_model = pet._marshal()
    unmarshalled_marshalled_model = Pet._unmarshal(marshalled_model)
    assert marshalled_model == {'id': pet_id, 'name': pet_name, 'photoUrls': pet_photo_urls}
    assert isinstance(unmarshalled_marshalled_model, Pet)
    assert unmarshalled_marshalled_model.id == pet_id
    assert unmarshalled_marshalled_model.name == pet_name
    assert unmarshalled_marshalled_model.photoUrls == pet_photo_urls