how to change the mulligan setting for keeping the cards

I know there is a way to not to keep the card by modifying the "DefaultRoutine.cs", such as "_mulliganRules.Add(new Tuple<string, string>("mulliganData.UserClass == TAG_CLASS.HUNTER", "card.Entity.Id == \"DS1_184\""));"

But how can I keep the card I want?

Can somebody help me?

how to change the mulligan setting for keeping the cards