docstr: Can older notebooks be opened without modification?
code: def test_read(self):
      """Can older notebooks be opened without modification?"""
  
      # Open a version 3 notebook.  Make sure it is still version 3.
      with self.fopen("test3.ipynb", "r") as f:
          nb = read(f)
      (major, minor) = get_version(nb)
      self.assertEqual(major, 3)
  
      # Open a version 2 notebook.  Make sure it is still version 2.
      with self.fopen("test2.ipynb", "r") as f:
          nb = read(f)
      (major, minor) = get_version(nb)
      self.assertEqual(major, 2)
  
file_path: nbformat/tests/test_reader.py
imports: from __future__ import annotations
  from nbformat.reader import get_version, read
  from nbformat.validator import ValidationError
  from .base import TestsBase
label_desc: Use image node_id 1 for calling the TestReader obj's underlying member method code with example usage: obj.test_read() without return types