W3 Lec9: Nonmax suppression for each class

Can anybody explain how exactly do we achieve the last point mentioned here i.e. “For each class use non - max suppression”
The output y contains values for different classes (here 3).
How can we run non max for each separate class.
A step by step explanation will be helpful

Since we have class labels for each of the bounding boxes, run non-max suppression for bounding boxes per class, seperately.

Please see this topic as well.