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 _rootsanddirs(kindpats):
    """Returns roots and exact directories from patterns.

    roots are directories to match recursively, whereas exact directories should
    be matched non-recursively. The returned (roots, dirs) tuple will also
    include directories that need to be implicitly considered as either, such as
    parent directories.

    >>> _rootsanddirs(
    ...     [(b'glob', b'g/h/*', b''), (b'glob', b'g/h', b''),
    ...      (b'glob', b'g*', b'')])
    (['g/h', 'g/h', ''], ['', 'g'])
    >>> _rootsanddirs(
    ...     [(b'rootfilesin', b'g/h', b''), (b'rootfilesin', b'', b'')])
    ([], ['g/h', '', '', 'g'])
    >>> _rootsanddirs(
    ...     [(b'relpath', b'r', b''), (b'path', b'p/p', b''),
    ...      (b'path', b'', b'')])
    (['r', 'p/p', ''], ['', 'p'])
    >>> _rootsanddirs(
    ...     [(b'relglob', b'rg*', b''), (b're', b're/', b''),
    ...      (b'relre', b'rr', b'')])
    (['', '', ''], [''])
    """
    r, d = _patternrootsanddirs(kindpats)

    # Append the parents as non-recursive/exact directories, since they must be
    # scanned to get to either the roots or the other exact directories.
    d.extend(sorted(util.dirs(d)))
    d.extend(sorted(util.dirs(r)))

    return r, d