Create and test a Set class to represent a classical set. Your sets should support the following methods:
Set(elements) Create a set (elements is the initial list of items in the set).
addElement(x) Adds x to the set.
deleteElement(x) Removes x from the set, if present. If x is not in the set, the set is left unchanged.
member(x) Returns true if x is in the set and false otherwise.
intersection(set2) Returns a new set containing just those elements that are common to this set and set2.
union(set2) Returns a new set containing all of elements that are in this set, set2, or both.
subtract(set2) Returns a new set containing all the elements of this set that are not in set2.