old_contents: from stylo.doc.builder import Notebook, NotebookCell
  
  
  class TestNotebook:
      """Tests for the :code:`Notebook` class."""
  
      def test_to_json(self):
          """Ensure that we can convert a :code:`Notebook` instance into a valid
          notebook."""
  
          expected = {
              "nbformat": 4,
              "nbformat_minor": 2,
              "metadata": {},
              "cells": [
                  {
                      "cell_type": "code",
                      "execution_count": None,
                      "metadata": {},
                      "outputs": [],
                      "source": [],
                  }
              ],
          }
  
          cell = NotebookCell.code()
          nb = Notebook.fromcells([cell])
  
          assert expected == nb.json
  
new_contents: from stylo.doc.builder import Notebook, NotebookCell
  
  
  class TestNotebook:
      """Tests for the :code:`Notebook` class."""
  
      def test_to_json(self):
          """Ensure that we can convert a :code:`Notebook` instance into a valid
          notebook."""
  
          expected = {
              "nbformat": 4,
              "nbformat_minor": 2,
              "metadata": {},
              "cells": [
                  {
                      "cell_type": "code",
                      "execution_count": None,
                      "metadata": {},
                      "outputs": [],
                      "source": ["\n"],
                  },
                  {"cell_type": "markdown", "metadata": {}, "source": ["\n"]},
              ],
          }
  
          code = NotebookCell.code()
          markdown = NotebookCell.markdown()
          nb = Notebook.fromcells([code, markdown])
  
          assert expected == nb.json
  
subject: Fix test