input: Write a function to find the union of two given lists. The function should return a set containing all unique elements from both lists.
  
  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([], [3, 4, 5, 6, 7]) == {3, 4, 5, 6, 7}
  assert unionList([1, 2, 3, 4, 5], []) == {1, 2, 3, 4, 5}
  assert unionList([], []) == set()
output: def unionList(list1, list2):
      return set(list1 + list2)