How to write populator for Map

Hi Experts,

I have Map to be converted from Model object to Data Object. Map contains userModel as key , and list of users Wishlist(Wishlist2Model)

Now I want to write populator to convert the map of these model object to Data.

As of now, I know how to write populator of list of model object. but now it is for map of model

Any suggestions

Thanks in advance