How to use the weasyprint.css.properties.Dimension function in weasyprint

),
    b5=(
        Dimension(176, 'mm'),
        Dimension(250, 'mm'),
    ),
    b4=(
        Dimension(250, 'mm'),
        Dimension(353, 'mm'),
    ),
    letter=(
        Dimension(8.5, 'in'),
        Dimension(11, 'in'),
    ),
    legal=(
        Dimension(8.5, 'in'),
        Dimension(14, 'in'),
    ),
    ledger=(
        Dimension(11, 'in'),
        Dimension(17, 'in'),
    ),
)
# In "portrait" orientation.
for w, h in PAGE_SIZES.values():
    assert w.value < h.value

INITIAL_PAGE_SIZE = PAGE_SIZES['a4']
INITIAL_VALUES['size'] = tuple(
    d.value * LENGTHS_TO_PIXELS[d.unit] for d in INITIAL_PAGE_SIZE)


def _computing_order():

def get_length(token, negative=True, percentage=False):
    """Parse a  token."""
    if percentage and token.type == 'percentage':
        if negative or token.value >= 0:
            return Dimension(token.value, '%')
    if token.type == 'dimension' and token.unit in LENGTH_UNITS:
        if negative or token.value >= 0:
            return Dimension(token.value, token.unit)
    if token.type == 'number' and token.value == 0:
        return Dimension(0, None)

else:
            main_flex_direction = None
        resolve_percentages(child, containing_block, main_flex_direction)
        child.position_x = parent_box.content_box_x()
        child.position_y = parent_box.content_box_y()
        if child.min_width == 'auto':
            specified_size = (
                child.width if child.width != 'auto' else float('inf'))
            if isinstance(child, boxes.ParentBox):
                new_child = child.copy_with_children(child.children)
            else:
                new_child = child.copy()
            new_child.style = child.style.copy()
            new_child.style['width'] = 'auto'
            new_child.style['min_width'] = Dimension(0, 'px')
            new_child.style['max_width'] = Dimension(float('inf'), 'px')
            content_size = min_content_width(context, new_child, outer=False)
            child.min_width = min(specified_size, content_size)
        elif child.min_height == 'auto':
            # TODO: find a way to get min-content-height
            specified_size = (
                child.height if child.height != 'auto' else float('inf'))
            if isinstance(child, boxes.ParentBox):
                new_child = child.copy_with_children(child.children)
            else:
                new_child = child.copy()
            new_child.style = child.style.copy()
            new_child.style['height'] = 'auto'
            new_child.style['min_height'] = Dimension(0, 'px')
            new_child.style['max_height'] = Dimension(float('inf'), 'px')
            new_child = blocks.block_level_layout(
                context, new_child, float('inf'), child_skip_stack,

def line_height(token):
    """``line-height`` property validation."""
    if get_keyword(token) == 'normal':
        return 'normal'
    if token.type == 'number' and token.value >= 0:
        return Dimension(token.value, None)
    if token.type == 'percentage' and token.value >= 0:
        return Dimension(token.value, '%')
    elif token.type == 'dimension' and token.value >= 0:
        return get_length(token)

)

# http://www.w3.org/TR/css3-page/#size
# name=(width in pixels, height in pixels)
PAGE_SIZES = dict(
    a5=(
        Dimension(148, 'mm'),
        Dimension(210, 'mm'),
    ),
    a4=(
        Dimension(210, 'mm'),
        Dimension(297, 'mm'),
    ),
    a3=(
        Dimension(297, 'mm'),
        Dimension(420, 'mm'),
    ),
    b5=(
        Dimension(176, 'mm'),
        Dimension(250, 'mm'),
    ),
    b4=(
        Dimension(250, 'mm'),
        Dimension(353, 'mm'),
    ),
    letter=(
        Dimension(8.5, 'in'),
        Dimension(11, 'in'),
    ),
    legal=(
        Dimension(8.5, 'in'),
        Dimension(14, 'in'),

marker_text = counters.format_list_marker(
                counter_value, style['list_style_type'])
            box = boxes.TextBox.anonymous_from(box, marker_text)
            box.style['white_space'] = 'pre-wrap'
            children.append(box)

    if not children:
        return

    if parent_style['list_style_position'] == 'outside':
        marker_box = boxes.BlockBox.anonymous_from(box, children)
        # We can safely edit everything that can't be changed by user style
        # See https://drafts.csswg.org/css-pseudo-4/#marker-pseudo
        marker_box.style['position'] = 'absolute'
        if parent_style['direction'] == 'ltr':
            translate_x = properties.Dimension(-100, '%')
        else:
            translate_x = properties.Dimension(100, '%')
        translate_y = computed_values.ZERO_PIXELS
        marker_box.style['transform'] = (
            ('translate', (translate_x, translate_y)),)
    else:
        marker_box = boxes.InlineBox.anonymous_from(box, children)
    yield marker_box

),
    b4=(
        Dimension(250, 'mm'),
        Dimension(353, 'mm'),
    ),
    letter=(
        Dimension(8.5, 'in'),
        Dimension(11, 'in'),
    ),
    legal=(
        Dimension(8.5, 'in'),
        Dimension(14, 'in'),
    ),
    ledger=(
        Dimension(11, 'in'),
        Dimension(17, 'in'),
    ),
)
# In "portrait" orientation.
for w, h in PAGE_SIZES.values():
    assert w.value < h.value

INITIAL_PAGE_SIZE = PAGE_SIZES['a4']
INITIAL_VALUES['size'] = tuple(
    d.value * LENGTHS_TO_PIXELS[d.unit] for d in INITIAL_PAGE_SIZE)


def _computing_order():
    """Some computed values are required by others, so order matters."""
    first = [
        'font_stretch', 'font_weight', 'font_family', 'font_variant',
        'font_style', 'font_size', 'line_height']

),
    b4=(
        Dimension(250, 'mm'),
        Dimension(353, 'mm'),
    ),
    letter=(
        Dimension(8.5, 'in'),
        Dimension(11, 'in'),
    ),
    legal=(
        Dimension(8.5, 'in'),
        Dimension(14, 'in'),
    ),
    ledger=(
        Dimension(11, 'in'),
        Dimension(17, 'in'),
    ),
)
# In "portrait" orientation.
for w, h in PAGE_SIZES.values():
    assert w.value < h.value

INITIAL_PAGE_SIZE = PAGE_SIZES['a4']
INITIAL_VALUES['size'] = tuple(
    d.value * LENGTHS_TO_PIXELS[d.unit] for d in INITIAL_PAGE_SIZE)


def _computing_order():
    """Some computed values are required by others, so order matters."""
    first = [
        'font_stretch', 'font_weight', 'font_family', 'font_variant',
        'font_style', 'font_size', 'line_height', 'marks']

Dimension(250, 'mm'),
    ),
    b4=(
        Dimension(250, 'mm'),
        Dimension(353, 'mm'),
    ),
    letter=(
        Dimension(8.5, 'in'),
        Dimension(11, 'in'),
    ),
    legal=(
        Dimension(8.5, 'in'),
        Dimension(14, 'in'),
    ),
    ledger=(
        Dimension(11, 'in'),
        Dimension(17, 'in'),
    ),
)
# In "portrait" orientation.
for w, h in PAGE_SIZES.values():
    assert w.value < h.value

INITIAL_PAGE_SIZE = PAGE_SIZES['a4']
INITIAL_VALUES['size'] = tuple(
    d.value * LENGTHS_TO_PIXELS[d.unit] for d in INITIAL_PAGE_SIZE)


def _computing_order():
    """Some computed values are required by others, so order matters."""
    first = [
        'font_stretch', 'font_weight', 'font_family', 'font_variant',