How to use the ask-sdk-dynamodb-persistence-adapter.PartitionKeyGenerators.userId function in ask-sdk-dynamodb-persistence-adapter

it('should be able to add DynamoDbPersistenceAdapter with customization', () => {
        const skillConfig = StandardSkillFactory.init()
            .withTableName('testTable')
            .withAutoCreateTable(false)
            .withDynamoDbClient(new DynamoDB({apiVersion : 'latest'}))
            .withPartitionKeyGenerator(PartitionKeyGenerators.userId)
            .getSkillConfiguration();

        expect(skillConfig.persistenceAdapter).instanceOf(DynamoDbPersistenceAdapter);
    });
});