In Python, create the functions in parts 1 through 3. Part 2 should use the built-in set function while Part 3 should NOT.

1. def normalize(input_string):

• input: a string of text characters. Each character is called a token.

• output: an array of 'letters'. Each item in the array corresponds to a letter in input_string (in lowercase)

• for example, the input "O.K. #1 Python!" would generate the following list: ['o','k','p','y','t','h','o','n']

• don't try to replace, delete, or substitute -- if the 'token' is a letter it passes the test.

2. def find_missing_letters(sentence):

• the input sentence is an array/list (created from normalize())

• returns a sorted array of letters that are NOT in the sentence

• use the built in Python type set to solve

3. def find_missing_letters_algorithm(sentence):

• the input sentence is an array/list (created from normalize())

• returns a sorted array of letters that are NOT in the sentence

• you must NOT use the set type