1. accordion
2. accordion
3. springFast property

##### accordion library

1. Classes
2. Accordion
3. AccordionSection
4. ListController
5. SectionController
6. Mixins
7. CommonParams
8. Properties
9. listCtrl
10. springFast
11. Enums
12. ScrollIntoViewOfItems

# springFast top-level property Null safety

SpringDescription springFast
final

## Implementation

    final springFast = SpringDescription(mass: 1, stiffness: 200, damping: 30);