code: def test_parent_no_time_index_missing(
      self,
      es,
      extra_session_df,
      true_sessions_lti,
  ):
      # test dataframe without time index and not all instance have children
  
      # add session instance with no associated log instances
      es.replace_dataframe(
          dataframe_name="sessions", df=extra_session_df
      )
      es.add_last_time_indexes()
      # since sessions has no time index, default value is NaT
      true_sessions_lti[6] = pd.NaT
      sessions = es["sessions"]
  
      lti_name = sessions.ww.metadata.get("last_time_index")
      assert len(sessions[lti_name]) == 7
      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 6 for calling the TestLastTimeIndex obj's underlying member method code with example usage: obj.test_parent_no_time_index_missing(es, extra_session_df, true_sessions_lti) without return types