new_contents: #!/usr/bin/env python3
  
  """
  The Bifid Cipher uses a Polybius Square to encipher a message in a way that
  makes it fairly difficult to decipher without knowing the secret.
  
  https://www.braingle.com/brainteasers/codes/bifid.php
  """
  
  import numpy as np
  
  
  class BifidCipher:
      def __init__(self) -> None:
          SQUARE = [
              ["a", "b", "c", "d", "e"],
              ["f", "g", "h", "i", "k"],
              ["l", "m", "n", "o", "p"],
              ["q", "r", "s", "t", "u"],
              ["v", "w", "x", "y", "z"],
          ]
          self.SQUARE = np.array(SQUARE)
  
      def letter_to_numbers(self, letter: str) -> np.ndarray:
          """
          Return the pair of numbers that represents the given letter in the
          polybius square
  
          >>> np.array_equal(BifidCipher().letter_to_numbers('a'), [1,1])
          True
  
          >>> np.array_equal(BifidCipher().letter_to_numbers('u'), [4,5])
          True
          """
          index1, index2 = np.where(self.SQUARE == letter)
          indexes = np.concatenate([index1 + 1, index2 + 1])
          return indexes
  
      def numbers_to_letter(self, index1: int, index2: int) -> str:
          """
          Return the letter corresponding to the position [index1, index2] in
          the polybius square
  
          >>> BifidCipher().numbers_to_letter(4, 5) == "u"
          True
  
          >>> BifidCipher().numbers_to_letter(1, 1) == "a"
          True
          """
          letter = self.SQUARE[index1 - 1, index2 - 1]
          return letter
  
      def encode(self, message: str) -> str:
          """
          Return the encoded version of message according to the polybius cipher
  
          >>> BifidCipher().encode('testmessage') == 'qtltbdxrxlk'
          True
  
          >>> BifidCipher().encode('Test Message') == 'qtltbdxrxlk'
          True
  
          >>> BifidCipher().encode('test j') == BifidCipher().encode('test i')
          True
          """
          message = message.lower()
          message = message.replace(" ", "")
          message = message.replace("j", "i")
  
          first_step = np.empty((2, len(message)))
          for letter_index in range(len(message)):
              numbers = self.letter_to_numbers(message[letter_index])
  
              first_step[0, letter_index] = numbers[0]
              first_step[1, letter_index] = numbers[1]
  
          second_step = first_step.reshape(2 * len(message))
          encoded_message = ""
          for numbers_index in range(len(message)):
              index1 = int(second_step[numbers_index * 2])
              index2 = int(second_step[(numbers_index * 2) + 1])
              letter = self.numbers_to_letter(index1, index2)
              encoded_message = encoded_message + letter
  
          return encoded_message
  
      def decode(self, message: str) -> str:
          """
          Return the decoded version of message according to the polybius cipher
  
          >>> BifidCipher().decode('qtltbdxrxlk') == 'testmessage'
          True
          """
          message = message.lower()
          message.replace(" ", "")
          first_step = np.empty(2 * len(message))
          for letter_index in range(len(message)):
              numbers = self.letter_to_numbers(message[letter_index])
              first_step[letter_index * 2] = numbers[0]
              first_step[letter_index * 2 + 1] = numbers[1]
  
          second_step = first_step.reshape((2, len(message)))
          decoded_message = ""
          for numbers_index in range(len(message)):
              index1 = int(second_step[0, numbers_index])
              index2 = int(second_step[1, numbers_index])
              letter = self.numbers_to_letter(index1, index2)
              decoded_message = decoded_message + letter
  
          return decoded_message
  
subject: Add Bifid cipher (#5493)