code: def test_nan(self):
      x = pd.Series([np.nan, "", "This IS a STRING."])
      primitive_func = self.primitive().get_function()
      answers = [np.nan, 0.0, 9.0]
      np.testing.assert_array_equal(primitive_func(x), answers)
  
file_path: featuretools/featuretools/tests/primitive_tests/natural_language_primitives_tests/test_upper_case_count.py
imports: import numpy
  import pandas
  from featuretools.primitives import UpperCaseCount
  from featuretools.tests.primitive_tests.utils import PrimitiveTestBase, find_applicable_primitives, valid_dfs
label_desc: Use image node_id 2 for calling the TestUpperCaseCount obj's underlying member method code with example usage: obj.test_nan() without return types