How to use the cairosvg.helpers.point function in CairoSVG

for letter in PATH_LETTERS:
        path_data = path_data.replace(letter, ' {} '.format(letter))
    path_data = normalize(path_data)

    bounding_box = EMPTY_BOUNDING_BOX
    previous_x = 0
    previous_y = 0
    letter = 'M'    # Move as default
    while path_data:
        path_data = path_data.strip()
        if path_data.split(' ', 1)[0] in PATH_LETTERS:
            letter, path_data = (path_data + ' ').split(' ', 1)

        if letter in 'aA':
            # Elliptical arc curve
            rx, ry, path_data = point(None, path_data)
            rotation, path_data = path_data.split(' ', 1)
            rotation = radians(float(rotation))

            # The large and sweep values are not always separated from the
            # following values, here is the crazy parser
            large, path_data = path_data[0], path_data[1:].strip()
            while not large[-1].isdigit():
                large, path_data = large + path_data[0], path_data[1:].strip()
            sweep, path_data = path_data[0], path_data[1:].strip()
            while not sweep[-1].isdigit():
                sweep, path_data = sweep + path_data[0], path_data[1:].strip()

            large, sweep = bool(int(large)), bool(int(sweep))

            x, y, path_data = point(None, path_data)

x, y, path_data = point(None, path_data)

            # Relative coordinate, convert to absolute
            if letter in 'lmt':
                x += previous_x
                y += previous_y

            # Extend bounding box with coordinate
            bounding_box = extend_bounding_box(bounding_box, ((x, y),))
            previous_x = x
            previous_y = y

        elif letter in 'qQsS':
            # Quadratic curve/Smooth curve
            x1, y1, path_data = point(None, path_data)
            x, y, path_data = point(None, path_data)

            # Relative coordinates, convert to absolute
            if letter in 'qs':
                x1 += previous_x
                y1 += previous_y
                x += previous_x
                y += previous_y

            # Extend bounding box with coordinates
            bounding_box = extend_bounding_box(
                bounding_box, ((x1, y1), (x, y)))
            previous_x = x
            previous_y = y

        elif letter in 'vV':
            # Vertical line

elif letter == 'm':
            # Current point relative move
            x, y, string = point(surface, string)
            surface.context.rel_move_to(x, y)
            current_point = current_point[0] + x, current_point[1] + y

        elif letter == 'M':
            # Current point move
            x, y, string = point(surface, string)
            surface.context.move_to(x, y)
            current_point = x, y

        elif letter == 'q':
            # Relative quadratic curve
            x1, y1 = 0, 0
            x2, y2, string = point(surface, string)
            x3, y3, string = point(surface, string)
            xq1, yq1, xq2, yq2, xq3, yq3 = quadratic_points(
                x1, y1, x2, y2, x3, y3)
            surface.context.rel_curve_to(xq1, yq1, xq2, yq2, xq3, yq3)
            node.vertices.append((0, 0))
            current_point = current_point[0] + x3, current_point[1] + y3

        elif letter == 'Q':
            # Quadratic curve
            x1, y1 = current_point
            x2, y2, string = point(surface, string)
            x3, y3, string = point(surface, string)
            xq1, yq1, xq2, yq2, xq3, yq3 = quadratic_points(
                x1, y1, x2, y2, x3, y3)
            surface.context.curve_to(xq1, yq1, xq2, yq2, xq3, yq3)
            node.vertices.append((0, 0))

def polyline(surface, node):
    """Draw a polyline ``node``."""
    points = normalize(node.get('points', ''))
    if points:
        x, y, points = point(surface, points)
        surface.context.move_to(x, y)
        node.vertices = [(x, y)]
        while points:
            x_old, y_old = x, y
            x, y, points = point(surface, points)
            angle = point_angle(x_old, y_old, x, y)
            node.vertices.append((pi - angle, angle))
            surface.context.line_to(x, y)
            node.vertices.append((x, y))

def polyline(surface, node):
    """Draw a polyline ``node``."""
    points = normalize(node.get('points', ''))
    if points:
        x, y, points = point(surface, points)
        surface.context.move_to(x, y)
        node.vertices = [(x, y)]
        while points:
            x_old, y_old = x, y
            x, y, points = point(surface, points)
            angle = point_angle(x_old, y_old, x, y)
            node.vertices.append((pi - angle, angle))
            surface.context.line_to(x, y)
            node.vertices.append((x, y))

x1, y1 = current_point
            x2, y2, string = point(surface, string)
            x3, y3, string = point(surface, string)
            xq1, yq1, xq2, yq2, xq3, yq3 = quadratic_points(
                x1, y1, x2, y2, x3, y3)
            surface.context.curve_to(xq1, yq1, xq2, yq2, xq3, yq3)
            node.vertices.append((0, 0))
            current_point = x3, y3

        elif letter == 's':
            # Relative smooth curve
            x, y = current_point
            x1 = x3 - x2 if last_letter in 'csCS' else 0
            y1 = y3 - y2 if last_letter in 'csCS' else 0
            x2, y2, string = point(surface, string)
            x3, y3, string = point(surface, string)
            node.vertices.append((
                point_angle(x2, y2, x1, y1), point_angle(x2, y2, x3, y3)))
            surface.context.rel_curve_to(x1, y1, x2, y2, x3, y3)
            current_point = current_point[0] + x3, current_point[1] + y3

            # Save absolute values for x and y, useful if next letter is s or S
            x1 += x
            x2 += x
            x3 += x
            y1 += y
            y2 += y
            y3 += y

        elif letter == 'S':
            # Smooth curve
            x, y = current_point

def bounding_box_polyline(surface, node):
    """Get the bounding box of a ``polyline`` or ``polygon`` node."""
    bounding_box = EMPTY_BOUNDING_BOX
    points = []
    normalized_points = normalize(node.get('points', ''))
    while normalized_points:
        x, y, normalized_points = point(surface, normalized_points)
        points.append((x, y))
    return extend_bounding_box(bounding_box, points)