Function setHeadingCollapse

setHeadingCollapse(
    cell: Cell<ICellModel>,
    collapsing: boolean,
    notebook: StaticNotebook,
): number
Set the given cell and ** all "child" cells ** to the given collapse / expand if cell is a markdown header.
Parameters
- cell: Cell<ICellModel>
  The cell
- collapsing: boolean
  Whether to collapse or expand the cell
- notebook: StaticNotebook
  The target notebook widget.
Returns number
- Defined in packages/notebook/src/actions.tsx:2074