src/vs/workbench/api/common/extHostNotebookDocument.ts/ExtHostNotebookDocument/_validateRange
class ExtHostNotebookDocument:	private _validateRange(range: vscode.NotebookRange): vscode.NotebookRange {
		let start = range.start | 0;
		let end = range.end | 0;
		if (start < 0) {
			start = 0;
		}
		if (end > this._cells.length) {
			end = this._cells.length;
		}
		return range.with({ start, end });
	}