code: def test_numpy_masked_json_encoding(self):
      l = [1, 2, np.ma.core.masked]
      j1 = _json.dumps(l, cls=utils.PlotlyJSONEncoder)
      print(j1)
      assert j1 == "[1, 2, null]"
  
imports: import datetime
  import math
  import decimal
  from datetime import datetime
  from unittest import TestCase
  from time import time
  import pytest
  import numpy
  import pandas
  import pytz
  from pandas.testing import assert_series_equal
  import json
  import os
  import base64
  from plotly import optional_imports, utils
  import plotly.graph_objects
  from plotly.graph_objs import Scatter, Scatter3d, Figure, Data
  from plotly.utils import get_by_path
  from PIL import Image
label_desc: Use image node_id 16 for calling the TestJSONEncoder obj's underlying member method code with example usage: obj.test_numpy_masked_json_encoding() without return types