input: from typing import List
  
  
  def unionList(list1: List[int], list2: List[int]) -> set:
      """ Return the union of two lists.
      >>> unionList([1, 2, 3, 4, 5], [3, 4, 5, 6, 7])
      {1, 2, 3, 4, 5, 6, 7}
      >>> unionList([], [1, 2, 3])
      {1, 2, 3}
      """
output:     return set(list1) | set(list2)