code: def test_categorical_nan_equality(self):
      cat = Series(Categorical(["a", "b", "c", np.nan]))
      expected = Series([True, True, True, False])
      result = cat == cat
      tm.assert_series_equal(result, expected)
  
imports: import numpy
  from pandas import Categorical, Series
  import pandas._testing
label_desc: Use image node_id 1 for calling the TestCategoricalComparisons obj's underlying member method code with example usage: obj.test_categorical_nan_equality() without return types