How to use the cairosvg.parser.Tree function in CairoSVG

def test_low_level_api():
    """Test the low-level Python API with various parameters."""
    _png_filename, svg_filename = FILES[0]
    expected_content = cairosvg.svg2png(url=svg_filename)

    # Same as above, longer version
    tree = cairosvg.parser.Tree(url=svg_filename)
    file_like = io.BytesIO()
    surface = cairosvg.surface.PNGSurface(tree, file_like, 96)
    surface.finish()
    assert file_like.getvalue() == expected_content

    png_result = png.Reader(bytes=expected_content).read()
    expected_width, expected_height, _, _ = png_result

    # Abstract surface
    surface = cairosvg.surface.PNGSurface(tree, None, 96)
    assert surface.width == expected_width
    assert surface.height == expected_height
    assert cairo.SurfacePattern(surface.cairo).get_surface() is surface.cairo
    assert_raises(TypeError, cairo.SurfacePattern, 'Not a cairo.Surface.')

def use(surface, node):
    """Draw the content of another SVG node."""
    surface.context.save()
    surface.context.translate(
        size(surface, node.get('x'), 'x'), size(surface, node.get('y'), 'y'))
    if 'x' in node:
        del node['x']
    if 'y' in node:
        del node['y']
    if 'viewBox' in node:
        del node['viewBox']
    if 'mask' in node:
        del node['mask']
    href = parse_url(node.get_href()).geturl()
    tree = Tree(
        url=href, url_fetcher=node.url_fetcher, parent=node,
        tree_cache=surface.tree_cache, unsafe=node.unsafe)

    if not match_features(tree.xml_tree):
        surface.context.restore()
        return

    if tree.tag in ('svg', 'symbol'):
        # Explicitely specified
        # http://www.w3.org/TR/SVG11/struct.html#UseElement
        tree.tag = 'svg'
        if 'width' in node and 'height' in node:
            tree['width'], tree['height'] = node['width'], node['height']

    surface.draw(tree)
    node.get('fill', None)

if len(image_bytes) < 5:
        return

    x, y = size(surface, node.get('x'), 'x'), size(surface, node.get('y'), 'y')
    width = size(surface, node.get('width'), 'x')
    height = size(surface, node.get('height'), 'y')

    if image_bytes[:4] == b'\x89PNG' and not surface.map_image:
        png_file = BytesIO(image_bytes)
    elif (image_bytes[:5] in (b'

def draw(self, context, concrete_width, concrete_height, _image_rendering):
        try:
            svg = ScaledSVGSurface(
                cairosvg.parser.Tree(
                    bytestring=self._svg_data, url=self._base_url,
                    url_fetcher=self._cairosvg_url_fetcher),
                output=None, dpi=96, output_width=concrete_width,
                output_height=concrete_height)
            if svg.width and svg.height:
                context.scale(
                    concrete_width / svg.width, concrete_height / svg.height)
                context.set_source_surface(svg.cairo)
                context.paint()
        except Exception as e:
            LOGGER.error(
                'Failed to draw an SVG image at %s : %s', self._base_url, e)

self.text = handle_white_spaces(element.etree_element.text, preserve)
        if trailing_space and not preserve:
            self.text = self.text.lstrip(' ')
        original_rotate = rotations(self)
        rotate = list(original_rotate)
        if original_rotate:
            pop_rotation(self, original_rotate, rotate)
        if self.text:
            trailing_space = self.text.endswith(' ')
        for child_element in element.iter_children():
            child = child_element.etree_element
            if child.tag in ('{http://www.w3.org/2000/svg}tref', 'tref'):
                href = child.get(
                    '{http://www.w3.org/1999/xlink}href', child.get('href'))
                url = parse_url(href).geturl()
                child_tree = Tree(
                    url=url, url_fetcher=self.url_fetcher, parent=self,
                    unsafe=self.unsafe)
                child_tree.clear()
                child_tree.update(self)
                child_node = Node(
                    child_element, self.style, self.url_fetcher,
                    parent=child_tree, parent_children=True,
                    unsafe=self.unsafe)
                child_node.tag = 'tspan'
                # Retrieve the referenced node and get its flattened text
                # and remove the node children.
                child = child_tree.xml_tree
                child.text = flatten(child)
                child_element = cssselect2.ElementWrapper.from_xml_root(child)
            else:
                child_node = Node(

def use(self, node):
        """Draw the content of another SVG file."""
        self.context.save()
        self.context.translate(size(node.get("x")), size(node.get("y")))
        if "x" in node:
            del node["x"]
        if "y" in node:
            del node["y"]
        if "viewBox" in node:
            del node["viewBox"]
        href = node.get("{http://www.w3.org/1999/xlink}href")
        tree = Tree(href, node)
        self._set_context_size(*node_format(tree))
        self.draw(tree)
        self.context.restore()
        # Restore twice, because draw does not restore at the end of svg tags
        self.context.restore()

if len(image_bytes) < 5:
        return

    x, y = size(surface, node.get('x'), 'x'), size(surface, node.get('y'), 'y')
    width = size(surface, node.get('width'), 'x')
    height = size(surface, node.get('height'), 'y')

    if image_bytes[:4] == b'\x89PNG':
        png_file = BytesIO(image_bytes)
    elif (image_bytes[:5] in (b'

def update_def_href(surface, def_name, def_dict):
    """Update the attributes of the def according to its href attribute."""
    def_node = def_dict[def_name]
    href = parse_url(def_node.get_href()).fragment
    if href in def_dict:
        update_def_href(surface, href, def_dict)
        href_node = def_dict[href]
        def_dict[def_name] = Tree(
            url='#{}'.format(def_name), url_fetcher=def_node.url_fetcher,
            parent=href_node, parent_children=(not def_node.children),
            tree_cache=surface.tree_cache, unsafe=def_node.unsafe)
        # Inherit attributes generally not inherited
        for key, value in href_node.items():
            if key not in def_dict[def_name]:
                def_dict[def_name][key] = value