def METHOD_NAME(predictions, output_directory, saved_keys, backend):
    predictions = predictions[[c for c in predictions.columns if c not in saved_keys]]
    npy_filename = os.path.join(output_directory, "{}.npy")
    numpy_predictions = to_numpy_dataset(predictions, backend)
    for k, v in numpy_predictions.items():
        k = k.replace("<", "[").replace(">", "]")  # Replace <UNK> and <PAD> with [UNK], [PAD]
        if k not in saved_keys:
            if has_remote_protocol(output_directory):
                with open_file(npy_filename.format(make_safe_filename(k)), mode="wb") as f:
                    np.save(f, v)
            else:
                np.save(npy_filename.format(make_safe_filename(k)), v)
            saved_keys.add(k)