src/vs/workbench/api/common/extHostNotebookKernels.ts/NotebookCellExecutionTask/verifyStateForOutput
class NotebookCellExecutionTask:	private verifyStateForOutput() {
		if (this._state === NotebookCellExecutionTaskState.Init) {
			throw new Error('Must call start before modifying cell output');
		}

		if (this._state === NotebookCellExecutionTaskState.Resolved) {
			throw new Error('Cannot modify cell output after calling resolve');
		}
	}