In Module 5- More Types , Dictionaries Questions there`s a question that

Question

Which of the following can`t be used as dictionary key?
answer is {2:4,3:9,4:16,}
but immediately in next Dictionary Functions
their is an example which indicates the same..dictionary declared as
squares = {1: 1, 2: 4, 3: "error", 4: 16,}
squares[8] = 64
squares[3] = 9
print(squares)
Output is given as
{1:1,2:4,3:9,4:16}
can anyone explain this?

Answer 1

The question asked if you could do like this:
{{2: 4, 3: 9, 4:16}: "some value"}
Where a dictionary was used as a key for another dictionary.
You can't.

Answer 2

You can find the answer on the previous page to that question on the first line.
A dictionary key must be immutable whereas dictionary is mutable so you cannot use that as a key.