src/vs/workbench/api/common/extHostNotebookDocument.ts/ExtHostNotebookDocument/_changeCellLanguage
class ExtHostNotebookDocument:	private _changeCellLanguage(index: number, newLanguageId: string): void {
		const cell = this._cells[index];
		if (cell.apiCell.document.languageId !== newLanguageId) {
			this._textDocuments.$acceptModelLanguageChanged(cell.uri, newLanguageId);
		}
	}