def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def test_nested_initializers(self):
        # test initializing nested structures
        class Phone(Structure):
            _fields_ = [("areacode", c_char*6),
                        ("number", c_char*12)]

        class Person(Structure):
            _fields_ = [("name", c_char * 12),
                        ("phone", Phone),
                        ("age", c_int)]

        p = Person(b"Someone", (b"1234", b"5678"), 5)

        self.assertEqual(p.name, b"Someone")
        self.assertEqual(p.phone.areacode, b"1234")
        self.assertEqual(p.phone.number, b"5678")
        self.assertEqual(p.age, 5)