Write a function that takes in a string as input and returns a list of the unique characters used in the string. Punctuation should not be counted as a unique character. For our purposes you may...

Extracted text: Write a function that takes in a string as input and returns a list of the unique characters used in the string. Punctuation should not be counted as a unique character. For our purposes you may consider the following characters as punctuation: .,;:?!"'- Your list should return all letters as lower case and sorted. So for example if the input is '(Happy days are here again!' your function should return the list ['a', 'd','e','g','h','i','n','p','r','s','y']