def METHOD_NAME():
    # This will test first that we can access all_data, and next that we can
    # access it multiple times and get the *same object*.
    ds = fake_amr_ds(fields=["density"], units=["g/cm**3"])
    dd = ds.all_data()
    assert_equal(ds.r[("gas", "density")], dd[("gas", "density")])
    # Now let's assert that it's the same object
    rho = ds.r[("gas", "density")]
    rho *= 2.0
    assert_equal(dd[("gas", "density")] * 2.0, ds.r[("gas", "density")])
    assert_equal(dd["gas", "density"] * 2.0, ds.r["gas", "density"])