Write letters_used(word) that returns the different letters of the word (lower case) as a sorted list.
letters_used('Banana')
→ ['a', 'b', 'n']letters_used('sql')
→ ['l', 'q', 's']Submit runs 4 tests, including hidden edge cases.
Each hint gives a little more help. Try on your own first.
Run your code to see the output here.