How to use the pycaption.geometry.Size function in pycaption

def test_point_is_relative(self):
        size_px = Size(30, UnitEnum.PIXEL)
        size_px2 = Size(30, UnitEnum.PIXEL)

        size_percent = Size(30, UnitEnum.PERCENT)
        size_percent2 = Size(30, UnitEnum.PERCENT)

        point_abs = Point(size_px, size_px2)
        point_mix = Point(size_percent, size_px)
        point_rel = Point(size_percent, size_percent2)

        self.assertFalse(point_abs.is_relative())
        self.assertFalse(point_mix.is_relative())
        self.assertTrue(point_rel.is_relative())

def test_stretch_is_relative(self):
        size_px = Size(30, UnitEnum.PIXEL)
        size_px2 = Size(30, UnitEnum.PIXEL)

        size_percent = Size(30, UnitEnum.PERCENT)
        size_percent2 = Size(30, UnitEnum.PERCENT)

        stretch_abs = Stretch(size_px, size_px2)
        stretch_mix = Stretch(size_percent, size_px)
        stretch_rel = Stretch(size_percent, size_percent2)

        self.assertFalse(stretch_abs.is_relative())
        self.assertFalse(stretch_mix.is_relative())
        self.assertTrue(stretch_rel.is_relative())

def test_layout_is_relative(self):
        empty_layout = Layout()

        self.assertTrue(empty_layout.is_relative())

        size_px = Size(30, UnitEnum.PIXEL)
        size_px2 = Size(30, UnitEnum.PIXEL)

        size_percent = Size(30, UnitEnum.PERCENT)
        size_percent2 = Size(30, UnitEnum.PERCENT)

        point_abs = Point(size_px, size_px2)
        point_rel = Point(size_percent, size_percent2)

        stretch_abs = Stretch(size_px, size_px2)
        stretch_rel = Stretch(size_percent, size_percent2)

        layout_abs = Layout(
            origin=point_abs,
            extent=stretch_abs,
            padding=None
        )

def test_size_is_valid(self):
        with self.assertRaises(TypeError):
            Size()

        with self.assertRaises(ValueError):
            Size(None, None)

def test_layout_is_relative(self):
        empty_layout = Layout()

        self.assertTrue(empty_layout.is_relative())

        size_px = Size(30, UnitEnum.PIXEL)
        size_px2 = Size(30, UnitEnum.PIXEL)

        size_percent = Size(30, UnitEnum.PERCENT)
        size_percent2 = Size(30, UnitEnum.PERCENT)

        point_abs = Point(size_px, size_px2)
        point_rel = Point(size_percent, size_percent2)

        stretch_abs = Stretch(size_px, size_px2)
        stretch_rel = Stretch(size_percent, size_percent2)

        layout_abs = Layout(
            origin=point_abs,
            extent=stretch_abs,
            padding=None
        )

def test_padding_is_relative(self):
        size_px = Size(30, UnitEnum.PIXEL)
        size_px2 = Size(30, UnitEnum.PIXEL)
        size_px3 = Size(30, UnitEnum.PIXEL)
        size_px4 = Size(30, UnitEnum.PIXEL)

        size_percent = Size(30, UnitEnum.PERCENT)
        size_percent2 = Size(30, UnitEnum.PERCENT)
        size_percent3 = Size(30, UnitEnum.PERCENT)
        size_percent4 = Size(30, UnitEnum.PERCENT)

        padding_abs = Padding(size_px, size_px2, size_px3, size_px4)
        padding_mix = Padding(size_px, size_px2, size_px3, size_percent)
        padding_rel = Padding(
            size_percent, size_percent2, size_percent3, size_percent4)

        self.assertFalse(padding_abs.is_relative())
        self.assertFalse(padding_mix.is_relative())
        self.assertTrue(padding_rel.is_relative())

def test_point_is_relative(self):
        size_px = Size(30, UnitEnum.PIXEL)
        size_px2 = Size(30, UnitEnum.PIXEL)

        size_percent = Size(30, UnitEnum.PERCENT)
        size_percent2 = Size(30, UnitEnum.PERCENT)

        point_abs = Point(size_px, size_px2)
        point_mix = Point(size_percent, size_px)
        point_rel = Point(size_percent, size_percent2)

        self.assertFalse(point_abs.is_relative())
        self.assertFalse(point_mix.is_relative())
        self.assertTrue(point_rel.is_relative())

def from_xml_attribute(cls, attribute):
        """Instantiate the class from a value of the type "4px" or "5%"
        or any number concatenated with a measuring unit (member of UnitEnum)

        :type attribute: unicode
        """
        horizontal, vertical = six.text_type(attribute).split(' ')
        horizontal = Size.from_string(horizontal)
        vertical = Size.from_string(vertical)

        return cls(horizontal, vertical)

def __sub__(self, other):
        if self.unit == other.unit:
            return Size(self.value - other.value, self.unit)
        else:
            raise ValueError("The sizes should have the same measure units.")

def fit_to_screen(self):
        """
        If extent is not set or if origin + extent > 100%, (re)calculate it
        based on origin. It is a pycaption fix for caption files that are
        technically valid but contain inconsistent settings that may cause
        long captions to be cut out of the screen.

        ATTENTION: This must be called on relativized objects (such as the one
        returned by as_percentage_of). All units are presumed to be percentages.
        """

        if self.origin:
            # Calculated values to be used if replacement is needed
            diff_horizontal = Size(100 - self.origin.x.value, UnitEnum.PERCENT)
            diff_vertical = Size(100 - self.origin.y.value, UnitEnum.PERCENT)
            if not self.extent:
                # Extent is not set, use the calculated values
                new_extent = Stretch(diff_horizontal, diff_vertical)
            else:
                # Extent is set but may have inconsistent values,
                # e.g. origin="35% 25%" extent="80% 80%", which would cause
                # captions to end horizontally at 115% and vertically at 105%,
                # which would result in them being cut out of the screen.
                # In this case, the horizontal and vertical values are
                # corrected so that origin + extent = 100%.
                bottom_right = self.origin.add_stretch(self.extent)

                found_absolute_unit = False
                if bottom_right.x.unit != UnitEnum.PERCENT:
                    found_absolute_unit = True