code: def test_join_self(self, join_type):
      index = date_range("1/1/2000", periods=10)
      joined = index.join(index, how=join_type)
      assert index is joined
  
file_path: pandas/pandas/tests/indexes/datetimes/test_join.py
imports: from datetime import datetime, timezone
  import numpy
  import pytest
  from pandas import DataFrame, DatetimeIndex, Index, Timestamp, date_range, period_range, to_datetime
  import pandas._testing
  from pandas.tseries.offsets import BDay, BMonthEnd
label_desc: Use image node_id 2 for calling the TestJoin obj's underlying member method code with example usage: obj.test_join_self(join_type) without return types