Reference: removeDuplicatesFromSet
removeDuplicatesFromSet(S) removes all duplicates from the set S, so it becomes a "true set". Example: Given a set S = {❨1, 2❩, ❨1, 2❩, ❨5, 8❩, ❨2, 9❩}, removeDuplicatesFromSet(S) will return { ❨1, 2❩, ❨5, 8❩, ❨2, 9❩ }.