def METHOD_NAME(fs):
    test_path = os.path.join(BASE_PATH, str(uuid.uuid4()) + '.npy')
    test_w = fs_write.NpyWriter(test_path, fs=fs)
    with open(test_path, 'w') as fout:
        fout.write('aardvark')
    with pytest.raises(IOError):
        test_w.add_data(5)