input: Write a function to find the union of two lists without duplicates. The function should return a set that contains elements from both lists. If either list is empty, the function should return the union of the non-empty list with an empty set.
  def unionList(list1, list2):
      return set(list1 + list2)
  
  assert unionList([1, 2, 3, 4, 5], [3, 4, 5, 6, 7]) == {1, 2, 3, 4, 5, 6, 7}
  assert unionList([1, 2, 3], []) == {1, 2, 3}
  assert unionList([], [4, 5, 6]) == {4, 5, 6}
  assert unionList([], []) == set()
output: def unionList(list1, list2):
      return set(list1 + list2)