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 from_file(
        self,
        filename: str,
        load: t.Callable[[t.IO[t.Any]], t.Mapping],
        silent: bool = False,
    ) -> bool:
        """Update the values in the config from a file that is loaded
        using the ``load`` parameter. The loaded data is passed to the
        :meth:`from_mapping` method.

        .. code-block:: python

            import toml
            app.config.from_file("config.toml", load=toml.load)

        :param filename: The path to the data file. This can be an
            absolute path or relative to the config root path.
        :param load: A callable that takes a file handle and returns a
            mapping of loaded data from the file.
        :type load: ``Callable[[Reader], Mapping]`` where ``Reader``
            implements a ``read`` method.
        :param silent: Ignore the file if it doesn't exist.

        .. versionadded:: 2.0
        """
        filename = os.path.join(self.root_path, filename)

        try:
            with open(filename) as f:
                obj = load(f)
        except OSError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
                return False

            e.strerror = f"Unable to load configuration file ({e.strerror})"
            raise

        return self.from_mapping(obj)