Set Methods
        Method	Description
        new Set()	Creates a new Set
        add()	Adds a new element to the Set
        delete()	Removes an element from a Set
        has()	Returns true if a value exists
        clear()	Removes all elements from a Set
        forEach()	Invokes a callback for each element
        values()	Returns an Iterator with all the values in a Set
        keys()	Same as values()
        entries()	Returns an Iterator with the [value,value] pairs from a Set
        Property	Description
        size	Returns the number elements in a Set