sideLength property Null safety

1. Flutter
2. quantizer_wu
3. QuantizerWu
4. sideLength property

QuantizerWu class

1. Constructors
2. QuantizerWu
3. Properties
4. cubes
5. hashCode
6. moments
7. momentsB
8. momentsG
9. momentsR
10. runtimeType
11. weights
12. Methods
13. computeMoments
14. constructHistogram
15. createBoxes
16. createResult
17. cut
18. maximize
19. noSuchMethod
20. quantize
21. toString
22. variance
23. Operators
24. operator ==
25. Static properties
26. maxIndex
27. sideLength
28. totalSize
29. Static methods
30. bottom
31. getIndex
32. top
33. volume
34. Constants
35. indexBits