How to evaluate multiclass problem using AUC?

Python
#1

I’m working on a machine learning project in which I’m evaluating the performance of a multiclass classification model. For this purpose, I’m using one common metric i.e. Area Under the Receiver Operating Characteristic (ROC) Curve (AUC). Previously, I was using the one-vs-rest (OvR) strategy to calculate the AUC for each class separately. Let me show you below:

Now, I got to know that there are many strategies available for calculating `AUC`. I’m not aware fully of them. Can someone explain some strategies that help me in my project?