def test_view_of_view(matrix_type, subset_func, subset_func2):
    adata = gen_adata((30, 15), X_type=matrix_type)
    adata.raw = adata
    if subset_func is single_subset:
        pytest.xfail("Other subset generating functions have trouble with this")
    var_s1 = subset_func(adata.var_names, min_size=4)
    var_view1 = adata[:, var_s1]
    var_s2 = subset_func2(var_view1.var_names)
    var_view2 = var_view1[:, var_s2]
    assert var_view2._adata_ref is adata
    obs_s1 = subset_func(adata.obs_names, min_size=4)
    obs_view1 = adata[obs_s1, :]
    obs_s2 = subset_func2(obs_view1.obs_names)
    assert adata[obs_s1, :][:, var_s1][obs_s2, :]._adata_ref is adata

    view_of_actual_copy = adata[:, var_s1].copy()[obs_s1, :].copy()[:, var_s2].copy()

    view_of_view_copy = adata[:, var_s1][obs_s1, :][:, var_s2].copy()

    assert_equal(view_of_actual_copy, view_of_view_copy, exact=True)
def _read_flo(file_name):
    """Read .flo file in Middlebury format"""
    # Code adapted from:
    # http://stackoverflow.com/questions/28013200/reading-middlebury-flow-files-with-python-bytes-array-numpy
    # Everything needs to be in little Endian according to
    # https://vision.middlebury.edu/flow/code/flow-code/README.txt
    with open(file_name, "rb") as f:
        magic = np.fromfile(f, "c", count=4).tobytes()
        if magic != b"PIEH":
            raise ValueError("Magic number incorrect. Invalid .flo file")

        w = int(np.fromfile(f, "<i4", count=1))
        h = int(np.fromfile(f, "<i4", count=1))
        data = np.fromfile(f, "<f4", count=2 * w * h)
        return data.reshape(h, w, 2).transpose(2, 0, 1)