code: def generic_decrypt(cipher_factory_map, ciphertext, key, iv):
      
      if backend is None:
          raise PysnmpCryptoError('Crypto backend not available')
  
      return _DECRYPT_MAP[backend](cipher_factory_map[backend],
                                   ciphertext, key, iv)
docs: Decrypt data using the available backend.
  
      :param dict cipher_factory_map: Dictionary that maps the backend name
          to a cipher factory callable for that backend
      :param bytes ciphertext: Ciphertext data to decrypt
      :param bytes key: Encryption key
      :param bytes IV: Initialization vector
      :returns: Decrypted plaintext
      :rtype: bytes