Function propagate_ui_target_cameras 

pub fn propagate_ui_target_cameras(
    commands: Commands<'_, '_>,
    default_ui_camera: DefaultUiCamera<'_, '_>,
    ui_scale: Res<'_, UiScale>,
    camera_query: Query<'_, '_, &Camera>,
    target_camera_query: Query<'_, '_, &UiTargetCamera>,
    ui_root_nodes: UiRootNodes<'_, '_>,
)