src/vs/workbench/contrib/notebook/browser/notebookEditor.ts/NotebookEditor/_loadNotebookEditorViewState
class NotebookEditor:	private _loadNotebookEditorViewState(input: NotebookEditorInput): INotebookEditorViewState | undefined {
		let result: INotebookEditorViewState | undefined;
		if (this.group) {
			result = this._editorMemento.loadEditorState(this.group, input.resource);
		}
		if (result) {
			return result;
		}
		// when we don't have a view state for the group/input-tuple then we try to use an existing
		// editor for the same resource.
		for (const group of this._editorGroupService.getGroups(GroupsOrder.MOST_RECENTLY_ACTIVE)) {
			if (group.activeEditorPane !== this && group.activeEditorPane instanceof NotebookEditor && group.activeEditor?.matches(input)) {
				return group.activeEditorPane._widget.value?.getEditorViewState();
			}
		}
		return;
	}