How to use the pyscroll.group.PyscrollGroup function in pyscroll

self.walls.append(pygame.Rect(
                object.x, object.y,
                object.width, object.height))

        # create new data source for pyscroll
        map_data = pyscroll.data.TiledMapData(tmx_data)

        # create new renderer (camera)
        self.map_layer = pyscroll.BufferedRenderer(map_data, screen.get_size(), clamp_camera=False, tall_sprites=1)
        self.map_layer.zoom = 2

        # pyscroll supports layered rendering.  our map has 3 'under' layers
        # layers begin with 0, so the layers are 0, 1, and 2.
        # since we want the sprite to be on top of layer 1, we set the default
        # layer for sprites as 2
        self.group = PyscrollGroup(map_layer=self.map_layer, default_layer=2)

        self.hero = Hero()

        # put the hero in the center of the map
        self.hero.position = self.map_layer.map_rect.center
        self.hero._position[0] += 200
        self.hero._position[1] += 400

        # add our hero to the group
        self.group.add(self.hero)

self.walls.append(pygame.Rect(
                object.x, object.y,
                object.width, object.height))

        # create new data source for pyscroll
        map_data = pyscroll.data.TiledMapData(tmx_data)

        # create new renderer (camera)
        self.map_layer = pyscroll.BufferedRenderer(map_data, screen.get_size())
        self.map_layer.zoom = 2

        # pyscroll supports layered rendering.  our map has 3 'under' layers
        # layers begin with 0, so the layers are 0, 1, and 2.
        # since we want the sprite to be on top of layer 1, we set the default
        # layer for sprites as 2
        self.group = PyscrollGroup(map_layer=self.map_layer, default_layer=2)

        self.hero = Hero()

        # put the hero in the center of the map
        self.hero.position = self.map_layer.map_rect.center

        # add our hero to the group
        self.group.add(self.hero)