code: def test_empty_string(self):
      primitive_func = self.primitive().get_function()
      names = pd.Series(
          [
              "Peter, Michael J",
              "",
              "Kate Elizabeth Brown-Jones",
          ],
      )
      answer = pd.Series(["Peter", np.nan, "Brown-Jones"], dtype=object)
      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 TestFullNameToLastName obj's underlying member method code with example usage: obj.test_empty_string() without return types