code: def test_to_json(self):
      json_str = make_viz_data_adapter().to_json()
      self.assertEqual(PAYLOAD, json.loads(json_str))
  
imports: import json
  from unittest import TestCase
  from scattertext.viz import VizDataAdapter
label_desc: Use image node_id 2 for calling the TestVizDataAdapter obj's underlying member method code with example usage: obj.test_to_json() without return types