ML basics - L2 regularization & Decision Region of MultiClassClassifier (python)

Appendix

Reference

https://vivek-singh.medium.com/an-introduction-to-gradient-descent-54775b55ba4f
https://jermwatt.github.io/machine_learning_refined/notes/7_Linear_multiclass_classification/7_2_OvA.html
https://www.cs.toronto.edu/~urtasun/courses/CSC411/07_multiclass.pdf