PartialProductList constructor Null safety

1. smooth_app
2. partial_product_list
3. PartialProductList
4. PartialProductList constructor

PartialProductList class

1. Constructors
2. PartialProductList
3. Properties
4. hashCode
5. runtimeType
6. totalSize
7. Methods
8. add
9. clear
10. getProducts
11. noSuchMethod
12. toString
13. Operators
14. operator ==