def test_normal(self):
     original = {
         1: {1,2,3},
         2: {1},
         3: {4,5}
     }
         
     actual_dict = original.copy()
     actual = MultiDict(actual_dict)
     
     assert actual.dict == actual_dict
     assert set(actual.items()) == {(1,1), (1,2), (1,3), (2,1), (3,4), (3,5)}
     assert set(actual.keys()) == {1, 2, 3}
     assert set(actual.values()) == {1, 2, 3, 4, 5}
     assert actual.invert() == {
         1: {1,2},
         2: {1},
         3: {1},
         4: {3},
         5: {3}
     }
 def test_empty(self):
     actual = MultiDict({})
     assert set(actual.items()) == set()
     assert set(actual.keys()) == set()
     assert set(actual.values()) == set()
     assert actual.invert() == {}