input: Write a function to find the union of two lists by combining them and removing duplicates. Return the result as a set.
  def unionList(list1, list2):
      return set(list1 + list2)
  
  list1 = [1, 2, 3, 4, 5]
  list2 = [3, 4, 5, 6, 7]
  assert unionList(list1, list2)=={1, 2, 3, 4, 5, 6, 7}
  
  list1 = [1, 2, 2, 3]
  list2 = [3, 4, 4, 5]
  assert unionList(list1, list2)=={1, 2, 3, 4, 5}
  
  list1 = []
  list2 = [3, 4, 5]
  assert unionList(list1, list2)=={3, 4, 5}
  
  list1 = [1, 1, 1]
  list2 = [2, 2, 2]
  assert unionList(list1, list2)=={1, 2}
output: def unionList(list1, list2):
      return set(list1 + list2)