dict1 = { (1, 2) : [1, 2], (3, 4) : [3, 4] }
dict2 = { ([1], [2]) : [1, 2], ([3], [4]) : [3, 4]]}
dict1 will be created successfully while dict2 will give errors because its keys contain tuples which contain lists inside them. Tuples which are being used as a key in a dictionary should not contain any mutable type object.