code: def decrypt(self, msg, alg='aes_128_cbc', padding='PKCS#7', b64dec=True):
          
          self.__class__._deprecation_notice()
          data = _base64.b64decode(msg) if b64dec else msg
  
          cipher, iv = self.build_cipher(alg=alg)
          decryptor = cipher.decryptor()
          res = decryptor.update(data)[self.AES_BLOCK_SIZE:]
          res += decryptor.finalize()
          if padding in ['PKCS#5', 'PKCS#7']:
              idx = bytearray(res)[-1]
              res = res[:-idx]
          return res
docs: :param key: The encryption key
          :param msg: Base64 encoded message to be decrypted
          :return: The decrypted message