def METHOD_NAME(encrypted_data_key):
    """
    _api_decrypt_response calls kms.decrypt with the
    configured data key as the CiphertextBlob kwarg.
    """
    kms_client = MagicMock()
    with patch.object(aws_kms, "_kms") as kms_getter:
        kms_getter.return_value = kms_client
        with patch.object(aws_kms, "_cfg_data_key", lambda: encrypted_data_key):
            aws_kms._api_decrypt()
            kms_client.decrypt.assert_called_with(CiphertextBlob=encrypted_data_key)