How to use the black.assert_stable function in black

def test_cantfit(self) -> None:
        source, expected = read_data("cantfit")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def test_import_spacing(self) -> None:
        source, expected = read_data("import_spacing")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def checkSourceFile(self, name: str) -> None:
        path = THIS_DIR.parent / name
        source, expected = read_data(str(path), data=False)
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())
        self.assertFalse(ff(path))

def test_comments3(self) -> None:
        source, expected = read_data("comments3")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def test_function_trailing_comma(self) -> None:
        source, expected = read_data("function_trailing_comma")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def test_string_quotes(self) -> None:
        source, expected = read_data("string_quotes")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())
        mode = black.FileMode(string_normalization=False)
        not_normalized = fs(source, mode=mode)
        self.assertFormatEqual(source, not_normalized)
        black.assert_equivalent(source, not_normalized)
        black.assert_stable(source, not_normalized, mode=mode)

def test_comments7(self) -> None:
        source, expected = read_data("comments7")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def test_comments2(self) -> None:
        source, expected = read_data("comments2")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def test_fmtonoff3(self) -> None:
        source, expected = read_data("fmtonoff3")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())

def test_function(self) -> None:
        source, expected = read_data("function")
        actual = fs(source)
        self.assertFormatEqual(expected, actual)
        black.assert_equivalent(source, actual)
        black.assert_stable(source, actual, black.FileMode())