src/vs/workbench/contrib/interactive/browser/interactiveDocumentService.ts/InteractiveDocumentService/willCreateInteractiveDocument
class InteractiveDocumentService:	willCreateInteractiveDocument(notebookUri: URI, inputUri: URI, languageId: string) {
		this._onWillAddInteractiveDocument.fire({
			notebookUri,
			inputUri,
			languageId
		});
	}