code: def test_sub_datetime_preserves_freq(self, tz_naive_fixture):
      # GH#48818
      dti = date_range("2016-01-01", periods=12, tz=tz_naive_fixture)
  
      res = dti - dti[0]
      expected = timedelta_range("0 Days", "11 Days")
      tm.assert_index_equal(res, expected)
      assert res.freq == expected.freq
  
imports: import pytest
  from pandas import Timedelta, TimedeltaIndex, Timestamp, date_range, timedelta_range
  import pandas._testing
label_desc: Use image node_id 2 for calling the TestDatetimeIndexArithmetic obj's underlying member method code with example usage: obj.test_sub_datetime_preserves_freq(tz_naive_fixture) without return types