How to use the approvaltests.get_default_namer function in approvaltests

def test_full(self):
        namer = get_default_namer()
        writer = StringWriter("b")
        reporter = ReporterForTesting()
        approver = FileApprover()
        approver.verify(namer, writer, reporter)
        self.assertTrue(reporter.called)

def verify_all_combinations(function_under_test, input_arguments, formatter=None, reporter=None):
    """Run func with all possible combinations of args and verify outputs against the recorded approval file.

    Args:
        function_under_test (function): function under test.
        input_arguments: list of values to test for each input argument.  For example, a function f(product, quantity)
            could be tested with the input_arguments [['water', 'cola'], [1, 4]], which would result in outputs for the
            following calls being recorded and verified: f('water', 1), f('water', 4), f('cola', 1), f('cola', 4).
        formatter (function): function for formatting the function inputs/outputs before they are recorded to an
            approval file for comparison.
        reporter (approvaltests.reporter.Reporter): an approval reporter.

    Raises:
        ApprovalException: if the results to not match the approved results.
    """
    namer = get_default_namer()
    verify_all_combinations_with_namer(function_under_test, input_arguments, namer, formatter, reporter)

def assert_equal_with_reporter(expected, actual, reporter=None):
    if actual == expected:
        return

    name = get_default_namer().get_file_name()
    expected_file = write_to_temporary_file(expected, name + '.expected.')
    actual_file = write_to_temporary_file(actual, name + '.actual.')
    get_reporter(reporter).report(actual_file, expected_file)
    raise AssertionError('expected != actual\n  actual: "{}"\nexpected: "{}"'.format(actual, expected))

def test_returns_none_when_files_are_same_files(self):
        namer = get_default_namer()
        writer = StringWriter("b")
        reporter = GenericDiffReporterFactory().get_first_working()
        approver = FileApprover()
        error = approver.verify(namer, writer, reporter)
        self.assertEqual(None, error)

def test_passes_for_func_accepting_one_arg_and_combination_of_one_arg(self):
        arg1_combinations = (1,)
        all_args_combinations = (arg1_combinations,)
        namer= get_default_namer()
        verify_all_combinations_with_namer(self.func, all_args_combinations, namer, reporter=self.reporter)

def test_returns_error_when_files_are_different(self):
        namer = get_default_namer()
        writer = StringWriter("b")
        reporter = ReporterForTesting()
        approver = FileApprover()
        error = approver.verify(namer, writer, reporter)
        self.assertEqual("Approval Mismatch", error)