Function layout_to_svg_group 

pub fn layout_to_svg_group(
    layout: &Layout,
    container_id: u64,
    options: SvgDrawOptions,
    title: &str,
) -> (Group, Rect)

Render only the item definitions used by this layout.

container_id is the caller’s external bin or sheet ID, as in export_layout_snapshot. It names the container_{id} group and prefixes item definition IDs, so several layouts can share one document.