src/vs/workbench/contrib/notebook/browser/contrib/outline/notebookOutline.ts/NotebookCellOutline/_getCellFirstNonEmptyLine
class NotebookCellOutline:	private _getCellFirstNonEmptyLine(cell: ICellViewModel) {
		const textBuffer = cell.textBuffer;
		for (let i = 0; i < textBuffer.getLineCount(); i++) {
			const firstNonWhitespace = textBuffer.getLineFirstNonWhitespaceColumn(i + 1);
			const lineLength = textBuffer.getLineLength(i + 1);
			if (firstNonWhitespace < lineLength) {
				return textBuffer.getLineContent(i + 1);
			}
		}

		return cell.getText().substring(0, 10_000);
	}