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❩ }.