How to use the weasyprint.css.utils.get_length function in weasyprint

def transform(tokens):
    """Validation for ``transform``."""
    if get_single_keyword(tokens) == 'none':
        return ()
    else:
        transforms = []
        for token in tokens:
            function = parse_function(token)
            if not function:
                return
            name, args = function

            if len(args) == 1:
                angle = get_angle(args[0])
                length = get_length(args[0], percentage=True)
                if name in ('rotate', 'skewx', 'skewy') and angle:
                    transforms.append((name, angle))
                elif name in ('translatex', 'translate') and length:
                    transforms.append((
                        'translate', (length, computed_values.ZERO_PIXELS)))
                elif name == 'translatey' and length:
                    transforms.append((
                        'translate', (computed_values.ZERO_PIXELS, length)))
                elif name == 'scalex' and args[0].type == 'number':
                    transforms.append(('scale', (args[0].value, 1)))
                elif name == 'scaley' and args[0].type == 'number':
                    transforms.append(('scale', (1, args[0].value)))
                elif name == 'scale' and args[0].type == 'number':
                    transforms.append(('scale', (args[0].value,) * 2))
                else:
                    return

transforms.append((
                        'translate', (computed_values.ZERO_PIXELS, length)))
                elif name == 'scalex' and args[0].type == 'number':
                    transforms.append(('scale', (args[0].value, 1)))
                elif name == 'scaley' and args[0].type == 'number':
                    transforms.append(('scale', (1, args[0].value)))
                elif name == 'scale' and args[0].type == 'number':
                    transforms.append(('scale', (args[0].value,) * 2))
                else:
                    return
            elif len(args) == 2:
                if name == 'scale' and all(a.type == 'number' for a in args):
                    transforms.append((name, tuple(arg.value for arg in args)))
                else:
                    lengths = tuple(
                        get_length(token, percentage=True) for token in args)
                    if name == 'translate' and all(lengths):
                        transforms.append((name, lengths))
                    else:
                        return
            elif len(args) == 6 and name == 'matrix' and all(
                    a.type == 'number' for a in args):
                transforms.append((name, tuple(arg.value for arg in args)))
            else:
                return
        return tuple(transforms)

def border_corner_radius(tokens):
    """Validator for the `border-*-radius` properties."""
    lengths = [
        get_length(token, negative=False, percentage=True) for token in tokens]
    if all(lengths):
        if len(lengths) == 1:
            return (lengths[0], lengths[0])
        elif len(lengths) == 2:
            return tuple(lengths)

def background_size(tokens):
    """Validation for ``background-size``."""
    if len(tokens) == 1:
        token = tokens[0]
        keyword = get_keyword(token)
        if keyword in ('contain', 'cover'):
            return keyword
        if keyword == 'auto':
            return ('auto', 'auto')
        length = get_length(token, negative=False, percentage=True)
        if length:
            return (length, 'auto')
    elif len(tokens) == 2:
        values = []
        for token in tokens:
            length = get_length(token, negative=False, percentage=True)
            if length:
                values.append(length)
            elif get_keyword(token) == 'auto':
                values.append('auto')
        if len(values) == 2:
            return tuple(values)

def border_spacing(tokens):
    """Validator for the `border-spacing` property."""
    lengths = [get_length(token, negative=False) for token in tokens]
    if all(lengths):
        if len(lengths) == 1:
            return (lengths[0], lengths[0])
        elif len(lengths) == 2:
            return tuple(lengths)

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)

def width_height(token):
    """Validation for the ``width`` and ``height`` properties."""
    length = get_length(token, negative=False, percentage=True)
    if length:
        return length
    if get_keyword(token) == 'auto':
        return 'auto'

def border_width(token):
    """Border, column rule and outline widths properties validation."""
    length = get_length(token, negative=False)
    if length:
        return length
    keyword = get_keyword(token)
    if keyword in ('thin', 'medium', 'thick'):
        return keyword

def length_or_precentage(token):
    """``padding-*`` properties validation."""
    length = get_length(token, negative=False, percentage=True)
    if length:
        return length

def column_width(token):
    """``column-width`` property validation."""
    length = get_length(token, negative=False)
    if length:
        return length
    keyword = get_keyword(token)
    if keyword == 'auto':
        return keyword