def __init__(self, *args, **kwargs):
        self.model_class = kwargs.pop('model_class', self.model_class)
        if kwargs not in 'instance' and not self.model_class:
            raise RuntimeError('ResourceIdentifierObjectsSerializer must be initialized with a model class.')
        super(ResourceIdentifierObjectSerializer, self).__init__(*args, **kwargs)
dataset/ETHPy150Open django-json-api/django-rest-framework-json-api/rest_framework_json_api/serializers.py/ResourceIdentifierObjectSerializer.__init__/swapped operands of `not in`