docs: def union(self,other):
          """
          Return a new DiscreteSet with the union of the two sets, i.e.
          all elements that are in self or in other.
  
          :param DiscreteSet other: Set to unite with
          :rtype: DiscreteSet
          """
          if self.everything:
              return self
          elif other.everything:
              return other
          else:
              return DiscreteSet(self.elements.union(other.elements))