src/vs/workbench/api/common/extHostTypes.ts/NotebookCellOutput/constructor
class NotebookCellOutput:	constructor(
		items: NotebookCellOutputItem[],
		idOrMetadata?: string | Record<string, any>,
		metadata?: Record<string, any>
	) {
		this.items = NotebookCellOutput.ensureUniqueMimeTypes(items, true);
		if (typeof idOrMetadata === 'string') {
			this.id = idOrMetadata;
			this.metadata = metadata;
		} else {
			this.id = generateUuid();
			this.metadata = idOrMetadata ?? metadata;
		}
	}