code: def test_some_nans(self):
      primitive_func = self.primitive().get_function()
      booleans = pd.Series(
          [
              True,
              False,
              True,
              False,
              True,
              True,
              False,
              False,
              True,
              True,
          ],
      )
      datetimes = pd.Series([np.nan] * 2)
      datetimes = pd.concat([datetimes, self.datetimes])
      datetimes = pd.concat([datetimes, pd.Series([np.nan] * 2)])
      datetimes = datetimes.reset_index(drop=True)
      answer = pd.Series(
          [
              np.nan,
              np.nan,
              np.nan,
              0,
              6,
              12,
              0,
              0,
              np.nan,
              np.nan,
          ],
      )
      given_answer = primitive_func(datetimes, booleans)
      assert given_answer.equals(answer)
  
file_path: featuretools/featuretools/tests/primitive_tests/transform_primitive_tests/test_cumulative_time_since.py
imports: from datetime import datetime
  import numpy
  import pandas
  from featuretools.primitives import CumulativeTimeSinceLastFalse, CumulativeTimeSinceLastTrue
  from featuretools.tests.primitive_tests.utils import PrimitiveTestBase, find_applicable_primitives, valid_dfs
label_desc: Use image node_id 4 for calling the TestCumulativeTimeSinceLastFalse obj's underlying member method code with example usage: obj.test_some_nans() without return types