code: def test_null(self):
      x = pd.Series([np.nan, pd.NA, None, '"test"'])
      actual = self.primitive().get_function()(x)
      expected = pd.Series([pd.NA, pd.NA, pd.NA, 1.0], dtype="Int64")
      pd.testing.assert_series_equal(
          actual, expected, check_names=False
      )
  
file_path: featuretools/featuretools/tests/primitive_tests/natural_language_primitives_tests/test_number_of_words_in_quotes.py
imports: import numpy
  import pandas
  import pytest
  from featuretools.primitives import NumberOfWordsInQuotes
  from featuretools.tests.primitive_tests.utils import PrimitiveTestBase, find_applicable_primitives, valid_dfs
label_desc: Use image node_id 7 for calling the TestNumberOfWordsInQuotes obj's underlying member method code with example usage: obj.test_null() without return types