Get the Plan Id or make it dynamic

we can create Plan on SparkSerivceProvider

Spark::plan('Special Licence', 'provider-id-1')
            ->price(19)
            ->features([
                'First', 'Second', 'Third'
            ]);

Which i want to do is consider plan as a product. Now i need to get the id of the this product/plan so i can use it as a foreign key.