shrinkWrap property Null safety

1. baguette
2. CollectionWidget
3. CollectionWidget<T extends Widget>
4. shrinkWrap property

CollectionWidget class

1. Constructors
2. CollectionWidget
3. Properties
4. direction
5. endFraction
6. hashCode
7. itemCount
8. itemForIndex
9. itemVisibility
10. key
11. onEnd
12. onStart
13. reverse
14. runtimeType
15. shrinkWrap
16. startFraction
17. visibilityFraction
18. Methods
19. createElement
20. createState
21. debugDescribeChildren
22. debugFillProperties
23. noSuchMethod
24. toDiagnosticsNode
25. toString
26. toStringDeep
27. toStringShallow
28. toStringShort
29. Operators
30. operator ==