code: def test_column_json_encoding(self):
      columns = [
          Column(numeric_list, "col 1"),
          Column(mixed_list, "col 2"),
          Column(np_list, "col 3"),
      ]
      json_columns = _json.dumps(
          columns,
          cls=_plotly_utils.utils.PlotlyJSONEncoder,
          sort_keys=True,
      )
      print(json_columns)
      assert (
          '[{"data": [1, 2, 3], "name": "col 1"}, '
          '{"data": [1, "A", "2014-01-05T00:00:00", '
          '"2014-01-05T01:01:01", '
          '"2014-01-05T01:01:01.000001"], '
          '"name": "col 2"}, '
          '{"data": [1, 2, 3, null, null, null, '
          '"2014-01-05T00:00:00"], "name": "col 3"}]' == json_columns
      )
  
file_path: plotly.py/packages/python/chart-studio/chart_studio/tests/test_optional/test_utils/test_utils.py
imports: import json
  from unittest import TestCase
  import _plotly_utils.utils
  from chart_studio.grid_objs import Column
  from datetime import datetime
  import numpy
label_desc: Use image node_id 1 for calling the TestJSONEncoder obj's underlying member method code with example usage: obj.test_column_json_encoding() without return types