Python

isValid(a_string) (2 pts) Takes a string a_string and returns True if a_string is a string that has exactly 26 characters and each of the letters 'a'/'A' -'Z' /'Z' appeared only once in either lower case or upper case, False otherwise Preconditions: You should not make any assumptions about the size or contents of a_string. Input a_string A Python string TE Output bool True if txt uniquely contains all the characters of the English alphabet, False otherwise Example: >>> isValid("qwertyuiopASDFGHJKLzxcvbnm') True >>> isValid("hello there, spring is here!') False >>> isValid('POIUYTqwer ASDFGHlkjZXCVBMN) True