Add optional params to methods in a trait scala

Question

I have a trait with a method that's being used by 3 different classes, in one of the classes, I would like to override the method to accept an additional param, is this possible? how would one go about this in scala?

PS: I am new to Scala

Desired example:

trait Iterator {
    def hasNext(a : String): 
}
class Iterator extends Iterator {
   override def hasNext(a : String, b: String) = {
     ...
   }
}