code: def test_nan(self):
      primitive_func = self.primitive().get_function()
      names = pd.Series(["Mr. Brown", np.nan, None])
      answer = pd.Series(["Mr", np.nan, np.nan])
      pd.testing.assert_series_equal(
          primitive_func(names), answer, check_names=False
      )
  
imports: import numpy
  import pandas
  from featuretools.primitives import FullNameToFirstName, FullNameToLastName, FullNameToTitle
  from featuretools.tests.primitive_tests.utils import PrimitiveTestBase, find_applicable_primitives, valid_dfs
label_desc: Use image node_id 3 for calling the TestFullNameToTitle obj's underlying member method code with example usage: obj.test_nan() without return types