code: def test_difference_freq(self, sort):
      # GH14323: difference of DatetimeIndex should not preserve frequency
  
      index = date_range("20160920", "20160925", freq="D")
      other = date_range("20160921", "20160924", freq="D")
      expected = DatetimeIndex(
          ["20160920", "20160925"], dtype="M8[ns]", freq=None
      )
      idx_diff = index.difference(other, sort)
      tm.assert_index_equal(idx_diff, expected)
      tm.assert_attr_equal("freq", idx_diff, expected)
  
      # preserve frequency when the difference is a contiguous
      # subset of the original range
      other = date_range("20160922", "20160925", freq="D")
      idx_diff = index.difference(other, sort)
      expected = DatetimeIndex(
          ["20160920", "20160921"], dtype="M8[ns]", freq="D"
      )
      tm.assert_index_equal(idx_diff, expected)
      tm.assert_attr_equal("freq", idx_diff, expected)
  
imports: from datetime import datetime, timezone
  import numpy
  import pytest
  import pytz
  import pandas.util._test_decorators
  import pandas
  from pandas import DataFrame, DatetimeIndex, Index, Series, Timestamp, bdate_range, date_range
  import pandas._testing
  from pandas.tseries.offsets import BMonthEnd, Minute, MonthEnd
label_desc: Use image node_id 18 for calling the TestDatetimeIndexSetOps obj's underlying member method code with example usage: obj.test_difference_freq(sort) without return types