code: def DecryptPrivateKey(self, encrypted_private_key):
          
          aes = AES.new(self._master_key, AES.MODE_CBC, self._iv)
          return aes.decrypt(encrypted_private_key)
docs: Decrypt the provided ciphertext with the initialized private key.
  
          Args:
              encrypted_private_key (byte string): the ciphertext to be decrypted.
  
          Returns:
              bytes: the ciphertext.