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 reset_interactive_output_stream(
        cls, interactive_output_stream, override_faulthandler_destination=True
    ):
        """Class state:

        - Overwrites `cls._interactive_output_stream`.
        OS state:
        - Overwrites the SIGUSR2 handler.

        This method registers a SIGUSR2 handler, which permits a non-fatal `kill -31 <pants pid>` for
        stacktrace retrieval. This is also where the the error message on fatal exit will be printed to.
        """
        try:
            # NB: mutate process-global state!
            # This permits a non-fatal `kill -31 <pants pid>` for stacktrace retrieval.
            if override_faulthandler_destination:
                faulthandler.register(
                    signal.SIGUSR2, interactive_output_stream, all_threads=True, chain=False
                )
            # NB: mutate the class variables!
            cls._interactive_output_stream = interactive_output_stream
        except ValueError:
            # Warn about "ValueError: IO on closed file" when the stream is closed.
            cls.log_exception(
                "Cannot reset interactive_output_stream -- stream (probably stderr) is closed"
            )