def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def test_optional_arguments(self):
        self.assertEqual(self.myfunc('a'), self.expected)
        self.assertEqual(self.myfunc('a', 5), self.expected)
        self.assertEqual(self.myfunc('a', second=5), self.expected)
        self.assertEqual(self.myfunc('a', 5, 5), self.expected)
        self.assertEqual(self.myfunc('a', fourth=[]), self.expected)