input: Write a function to find the union of two lists. The function should take two lists as input and return a set containing all unique elements from both lists. If either list is empty, the function should return an empty set.
  
  def unionList(list1, list2):
      if not list1 or not list2:
          return set()
      return set(list1 + list2)
  
  # Test cases
  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]) == set()
  assert unionList([1, 2, 3, 4, 5], []) == set()
  assert unionList([], []) == set()
output: def unionList(list1, list2):
      if not list1 or not list2:
          return set()
      return set(list1 + list2)