def METHOD_NAME():
    p = datasets.PyCMDS.wm_w2_w1_001
    data = wt.data.from_PyCMDS(p)
    data.create_constant("w3")
    p = os.path.join(here, "data")
    p = data.save(p)
    assert os.path.isfile(p)
    assert p.endswith(".wt5")
    new = wt.open(p)
    for k, v in data.attrs.items():
        assert_equal(new.attrs[k], v)
    for k, v in data.items():
        assert_equal(new[k], v)
    for axis in new.axes:
        assert getattr(new, axis.natural_name) is axis
    for channel in new.channels:
        assert getattr(new, channel.natural_name) is channel
    assert new.constant_names == ("w3",)
    data.close()
    new.close()
    os.remove(p)