src/vs/workbench/contrib/notebook/browser/viewModel/notebookViewModel.ts/NotebookViewModel/_pushIfAbsent
class NotebookViewModel:	private _pushIfAbsent(positions: IPosition[], p: IPosition) {
		const last = positions.length > 0 ? positions[positions.length - 1] : undefined;
		if (!last || last.lineNumber !== p.lineNumber || last.column !== p.column) {
			positions.push(p);
		}
	}