old_contents: import string
  
  
  class Atbash:
  
      PLAIN = 'abcdefghijklmnopqrstuvwxyz'
      PRIME = 'zyxwvutsrqponmlkjihgfedcba'
      CIPHER = dict(list(zip(list(PLAIN), list(PRIME))))
      EXCLUDE = set(string.punctuation + ' ')
  
      @staticmethod
      def encode(self, msg):
          return self.split_every_five(self, self.encoded(self, msg))
  
      @staticmethod
      def split_every_five(self, encoded):
          return ' '.join([encoded[i:i + 5] for i in range(0, len(encoded), 5)])
  
      @staticmethod
      def encoded(self, msg):
          return ''.join(([char if char.isdigit() else self.CIPHER[char]
                           for char in self.clean(self, msg)]))
  
      @staticmethod
      def clean(self, msg):
          return (char for char in msg.lower() if char not in self.EXCLUDE)
  
      @staticmethod
      def decode(self, msg):
          return self.encoded(self, msg)
  
  
  def encode(msg):
      return Atbash.encode(Atbash, msg)
  
  
  def decode(msg):
      return Atbash.decode(Atbash, msg)
  
new_contents: import string
  
  
  class Atbash:
  
      PLAIN = string.ascii_lowercase
      PRIME = ''.join(reversed(string.ascii_lowercase))
      CIPHER = dict(list(zip(list(PLAIN), list(PRIME))))
      EXCLUDE = set(string.punctuation + ' ')
  
      @staticmethod
      def encode(self, msg):
          return self.split_every_five(self, self.encoded(self, msg))
  
      @staticmethod
      def split_every_five(self, encoded):
          return ' '.join([encoded[i:i + 5] for i in range(0, len(encoded), 5)])
  
      @staticmethod
      def encoded(self, msg):
          return ''.join(([char if char.isdigit() else self.CIPHER[char]
                           for char in self.clean(self, msg)]))
  
      @staticmethod
      def clean(self, msg):
          return (char for char in msg.lower() if char not in self.EXCLUDE)
  
      @staticmethod
      def decode(self, msg):
          return self.encoded(self, msg)
  
  
  def encode(msg):
      return Atbash.encode(Atbash, msg)
  
  
  def decode(msg):
      return Atbash.decode(Atbash, msg)
  
subject: Replace alphabet with string.ascii_lowercase