input: Write a function to find the union of two lists by combining them and removing any duplicates. The function should return a set of the combined elements from both lists.
  
  assert unionList([1, 2, 3, 4, 5], [3, 4, 5, 6, 7])=={1, 2, 3, 4, 5, 6, 7}
  assert unionList([4, 9, 12], [3, 4, 5, 9])=={3, 4, 5, 9, 12}
  assert unionList([], [3, 4, 5])=={3, 4, 5}
  assert unionList([1, 2, 3], [])=={1, 2, 3}
  assert unionList([], [])==set()
output: def unionList(list1, list2):
      return set(list1).union(set(list2))