def METHOD_NAME(file_extension, tmpdir):
    x = np.arange(N_rows, dtype='i8')
    df = vaex.from_arrays(x=x, x2=-x)
    df['y'] = df.x**2
    path = tmpdir / f'test.{file_extension}'
    df.export(path)
    df = vaex.open(path)
    yield df