code: def test_write(self):
      s = writes(nb0)
      self.assertEqual(s, nb0_py)
  
imports: from __future__ import annotations
  from unittest import TestCase
  from nbformat.v2.nbpy import writes
  from .nbexamples import nb0, nb0_py
label_desc: Use image node_id 1 for calling the TestPy obj's underlying member method code with example usage: obj.test_write() without return types