class Message(object):
    def __init__(self, text):
        '''
        Initializes a Message object

        text (string): the message's text

        a Message object has two attributes:
            self.message_text (string, determined by input text)
            self.valid_words (list, determined using helper function load_words)
        '''
        self.message_text = text
        self.valid_words = load_words(WORDLIST_FILENAME)

    def get_message_text(self):
        '''
        Used to safely access self.message_text outside of the class

        Returns: self.message_text
        '''
        return  self.message_text

    def get_valid_words(self):
        '''
        Used to safely access a copy of self.valid_words outside of the class.
        This helps you avoid accidentally mutating class attributes.

        Returns: a COPY of self.valid_words
        '''
        return self.valid_words

    def build_shift_dict(self, shift):
        '''
        Creates a dictionary that can be used to apply a cipher to a letter.
        The dictionary maps every uppercase and lowercase letter to a
        character shifted down the alphabet by the input shift. The dictionary
        should have 52 keys of all the uppercase letters and all the lowercase
        letters only.

        shift (integer): the amount by which to shift every letter of the
        alphabet. 0 <= shift < 26

        Returns: a dictionary mapping a letter (string) to
                 another letter (string).
        '''
        lower_keys = list(string.ascii_lowercase)
        lower_values = list(string.ascii_lowercase)
        shift_lower_values = lower_values[shift:] + lower_values[:shift]

        upper_keys = list(string.ascii_uppercase)
        upper_values = list(string.ascii_uppercase)
        upper_shift_values = upper_values[shift:] + upper_values[:shift]


    def apply_shift(self, shift):
        '''
        Applies the Caesar Cipher to self.message_text with the input shift.
        Creates a new string that is self.message_text shifted down the
        alphabet by some number of characters determined by the input shift

        shift (integer): the shift with which to encrypt the message.
        0 <= shift < 26

        Returns: the message text (string) in which every character is shifted
             down the alphabet by the input shift
        '''
        pass #delete this line and replace with your code here