old_contents: import unittest
  
  class TestSets(unittest.TestCase):
    "Testing set functions"
  
    def test_dict_keys_as_set(self):
      stacks = {
        "Jake": 10785,
        "Mitch": 5555,
        "Natalie": 400,
        "Frannie": 6005 
      }
  
      self.assertTrue("Frannie" in set(stacks))
  
    def test_dict_values_as_set(self):
      hands = {
        "Jake": {'Ah', 'As'},
        "Mitch": {'Kh', 'Kc'},
        "Natalie": {'Ks', 'Qs'},
        "Frannie": {'Kd', 'Qd'} 
      }
  
      self.assertTrue('As' in hands['Jake'])
  
    def test_intersection(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      self.assertFalse(valid_users & {'Manish', 'Jake'})
      self.assertTrue(valid_users & {'Thomas', 'Jake'})
  
    def test_explicit_intersection(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      troublemaking_users = valid_users & troublemakers
      self.assertEqual(1, len(troublemaking_users))
  
    def test_union(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      set_of_all = valid_users | troublemakers;
      self.assertEqual(len(set_of_all), 5)
  
    def test_difference(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      users_in_good_standing = valid_users - troublemakers
      self.assertEqual(2, len(users_in_good_standing))
  
new_contents: import unittest
  
  class TestSets(unittest.TestCase):
    "Testing set functions"
  
    def test_dict_keys_as_set(self):
      stacks = {
        "Jake": 10785,
        "Mitch": 5555,
        "Natalie": 400,
        "Frannie": 6005 
      }
  
      self.assertTrue("Frannie" in set(stacks))
  
    def test_dict_values_as_set(self):
      hands = {
        "Jake": {'Ah', 'As'},
        "Mitch": {'Kh', 'Kc'},
        "Natalie": {'Ks', 'Qs'},
        "Frannie": {'Kd', 'Qd'} 
      }
  
      self.assertTrue('As' in hands['Jake'])
  
    def test_intersection(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      self.assertFalse(valid_users & {'Manish', 'Jake'})
      self.assertTrue(valid_users & {'Thomas', 'Jake'})
  
    def test_explicit_intersection(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      troublemaking_users = valid_users & troublemakers
      self.assertEqual(1, len(troublemaking_users))
  
    def test_union(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      set_of_all = valid_users | troublemakers;
      self.assertEqual(len(set_of_all), 5)
  
    def test_difference(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      users_in_good_standing = valid_users - troublemakers
      self.assertEqual(2, len(users_in_good_standing))
  
    def test_difference(self):
      valid_users = { 'Thomas', 'Richard', 'Harold' }
      troublemakers = { 'Thomas', 'Jake', 'Mitch' }
      easily_categorized = valid_users ^ troublemakers
      self.assertEqual(4, len(easily_categorized))
      self.assertFalse('Thomas' in easily_categorized)
  
subject: test xor