input: Write a function to find the union of two lists. The function should return a set containing all unique 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([1, 2, 3], [4, 5, 6]) == {1, 2, 3, 4, 5, 6}
  assert unionList([], [3, 4, 5]) == {3, 4, 5}
  assert unionList([10, 11], []) == {10, 11}
  assert unionList([1, 1, 2, 2], [2, 2, 3, 3]) == {1, 2, 3}
output: def unionList(list1, list2):
      return set(list1) | set(list2)