code: def test_parent_no_time_index(self, es, true_sessions_lti):
      # test dataframe without time index and all instances have children
      es.add_last_time_indexes()
      sessions = es["sessions"]
      lti_name = sessions.ww.metadata.get("last_time_index")
      assert len(sessions[lti_name]) == 6
      sorted_lti = to_pandas(sessions[lti_name]).sort_index()
      for v1, v2 in zip(sorted_lti, true_sessions_lti):
          assert (pd.isnull(v1) and pd.isnull(v2)) or v1 == v2
  
imports: from datetime import datetime
  import pandas
  import pytest
  from woodwork.logical_types import Categorical, Datetime, Integer
  from featuretools.entityset.entityset import LTI_COLUMN_NAME
  from featuretools.tests.testing_utils import to_pandas
  from featuretools.utils.gen_utils import Library, import_or_none
label_desc: Use image node_id 5 for calling the TestLastTimeIndex obj's underlying member method code with example usage: obj.test_parent_no_time_index(es, true_sessions_lti) without return types