Find key in dictionary with most unique values

I have a dictionary of lists:

dict_one = {'a': ['Hanks', 'Bob', 'Bill'], 'b': ['nation', 'nile', 'Jonas']}

the dictionary above was only an example it could be extremely long

I need to find to the key with the most unique set of names or words.

I need both the key and the actual length of the key

So far, I have been able to find the actual length of the unique list pretty easily with the code below:

print(max(len(set(x)) for x in dict_one.values()))

But now I am struggling with finding the key itself. I need to print the length and the key itself as said prior. For example, an output might look like this:

key: a
length: 3

>Solution :

you’re pretty close. did you know that max can take a key the same way that sort can? check this out:

max(dict_one.items(), key=lambda x: len(set(x[1])))